The Dangers of a Nuclear Iran

What to do about Iran's nuclear program is one of the most vexing foreign policy challenges confronting the Obama administration. This debate is increasingly characterized both by growing pessimism about whether the international community's diplomatic efforts and economic sanctions can prevent Iran from acquiring nuclear weapons and by guarded optimism that the consequences a nuclear-armed Iran are manageable. Writing in these pages last spring, James Lindsay and Ray Takeyh, both of the Council on Foreign Relations, maintained that the United States could contain Iran even if it developed a nuclear arsenal by establishing clear "redlines" that Tehran would not be allowed to cross without risking some type of retaliation. For example, if Iran used its nuclear weapons, transferred them to a third party, invaded its neighbors, or increased its support for terrorist groups such as Hamas and Hezbollah, the United States would be compelled to respond, although the measures it chose to adopt would not be specified in advance. This argument reflects the public position of many senior U.S. and European officials, as well as a number of prominent academics and defense intellectuals.

Yet this view is far too sanguine. Above all, it rests on the questionable assumptions that possessing nuclear weapons induces caution and restraint, that other nations in the Middle East would balance against Iran rather than bandwagon with it, that a nuclear-armed Iran would respect new redlines even though a conventionally armed Iran has failed to comply with similar warnings, and that further proliferation in the region could be avoided. It seems more likely that Iran would become increasingly aggressive once it acquired a nuclear capability, that the United States' allies in the Middle East would feel greatly threatened and so would increasingly accommodate Tehran, that the United States' ability to promote and defend its interests in the region would be diminished, and that further nuclear proliferation, with all the dangers that entails, would occur. The greatest concern in the near term would be that an unstable Iranian-Israeli nuclear contest could emerge, with a significant risk that either side would launch a first strike on the other despite the enormous risks and costs involved. Over the longer term, Saudi Arabia and other states in the Middle East might pursue their own nuclear capabilities, raising the possibility of a highly unstable regional nuclear arms race.

Furthermore, the strategy that appears to be emerging as the default solution to these troubling outcomes -- a combination of deterrence and extended deterrence -- has serious drawbacks, and these are often downplayed or, worse, ignored. The conventional wisdom holds that U.S. security commitments can keep Iran in check, prevent U.S. allies in the Middle East from accommodating Tehran, and dissuade them from pursuing nuclear weapons. Yet both the willingness and the ability of the United States to defend its partners in the region against a nuclear-armed Iran are questionable. The United States was able to deter a nuclear-armed Soviet Union during the Cold War, but the foundations of its security arrangements then -- formal treaty guarantees and large U.S. military deployments on the territory of its allies -- are unlikely to materialize again soon. Although members of the Obama administration have stated that no option, including military force, should be taken off the table, they have done little to create a credible military option that would discourage Iran from pursuing nuclear weapons or contain it if diplomatic isolation, economic sanctions, or redlines fail to yield the desired results and Iran obtains nuclear weapons. By deploying additional U.S. air and naval forces in the Middle East, the United States could bolster its diplomatic efforts with coercive leverage, lay the foundation for an extended deterrence regime, and give itself the means to use force if a military campaign turns out to be the least bad option.

IRAN, ISRAEL, AND THE BOMB

Given Israel's status as an assumed but undeclared nuclear weapons state, the most immediate consequence of Iran's crossing the nuclear threshold would be the emergence of an unstable bipolar nuclear competition in the Middle East. Given Israel's enormous quantitative and qualitative advantage in nuclear weapons -- its arsenal is estimated to consist of anywhere from 100 to more than 200 warheads, possibly including thermonuclear weapons -- Tehran might fear a disarming preventive or preemptive strike. During a crisis, then, the Iranian leadership might face a "use them or lose them" dilemma with respect to its nuclear weapons and resolve it by attacking first.

For their part, Israeli leaders might also be willing to strike first, despite the enormous risks. Israel's small size means that even a few nuclear detonations on its soil would be devastating; Iran's former president Ali Akbar Hashemi Rafsanjani was exaggerating only slightly when he claimed that "even one nuclear bomb inside Israel will destroy everything." Iran's nuclear arsenal is likely to be small at first and perhaps vulnerable to a preventive attack. Moreover, even if current and future Israeli missile defenses could not stop a full-scale premeditated attack by ballistic missiles, they might be effective against any retaliation Iran might launch if it were hit first. And the willingness to execute a preventive or preemptive strike when confronting a serious threat is a deeply ingrained element of Israel's strategic culture, as Israel demonstrated in its attacks against Egypt in 1956 and 1967, against Iraq's nuclear program in 1981, and against a suspected Syrian nuclear site in 2007. On the one occasion that Israel absorbed the first blow, in 1973, it came perilously close to defeat. In short, the early stages of an Iranian-Israeli nuclear competition would be unstable.

Even if Iran and Israel managed to avoid a direct conflict, Iran's nuclear weapons would remain a persistent source of instability in the Middle East. Tehran would almost certainly attempt to expand the size of its arsenal to enhance the survivability of its nuclear weapons. To that end, it would have a strong incentive to adopt the North Korean model of proliferation: negotiating with the international community while continuing to expand its stockpile. Tehran could also deflect international pressure to disarm by offering to relinquish its arsenal if Israel did so as well, exploiting the desire of U.S. President Barack Obama and other Western leaders to make progress toward a world without nuclear weapons. As Iran's arsenal became larger and its fear of retaliation declined, however, it might be increasingly willing to engage in more subtle but still dangerous forms of aggression, including heightened support for terrorist groups or coercive diplomacy.

Meanwhile, if Iran acquires nuclear weapons, Israel might face internal and external pressures to abandon its posture of nuclear opacity, that is, its policy of refusing to confirm or deny that it has nuclear weapons. Internal pressure would come from those who believe that declaring Israel's arsenal is necessary to deter an attack by Iran. External pressure would come from those who view an Israeli declaration as the first step toward regional nuclear disarmament. But if Israel did abandon its policy of nuclear opacity, cooperation between Israel and its Arab neighbors would be far more difficult, and a containment strategy against Iran would thus be more challenging to implement. Such a disclosure might also encourage other states in the region to pursue their own nuclear weapons programs. Although most of Israel's neighbors have been willing to accept its undeclared nuclear weapons program so far, the combination of a nuclear-armed Iran and an openly nuclear-armed Israel could alter their calculations -- due to a heightened sense of threat, a desire for prestige, domestic pressure, or all three.

FROM ISLAMABAD TO RIYADH

The reports of the Congressional Commission on the Strategic Posture of the United States and the Commission on the Prevention of Weapons of Mass Destruction Proliferation and Terrorism, as well as other analyses, have highlighted the risk that a nuclear-armed Iran could trigger additional nuclear proliferation in the Middle East, even if Israel does not declare its own nuclear arsenal. Notably, Algeria, Bahrain, Egypt, Jordan, Saudi Arabia, Turkey, and the United Arab Emirates -- all signatories to the Nuclear Nonproliferation Treaty (NPT) -- have recently announced or initiated nuclear energy programs. Although some of these states have legitimate economic rationales for pursuing nuclear power and although the low-enriched fuel used for power reactors cannot be used in nuclear weapons, these moves have been widely interpreted as hedges against a nuclear-armed Iran. The NPT does not bar states from developing the sensitive technology required to produce nuclear fuel on their own, that is, the capability to enrich natural uranium and separate plutonium from spent nuclear fuel. Yet enrichment and reprocessing can also be used to accumulate weapons-grade enriched uranium and plutonium -- the very loophole that Iran has apparently exploited in pursuing a nuclear weapons capability.

Developing nuclear weapons remains a slow, expensive, and difficult process, even for states with considerable economic resources, and especially if other nations try to constrain aspiring nuclear states' access to critical materials and technology. Without external support, it is unlikely that any of these aspirants could develop a nuclear weapons capability within a decade.

There is, however, at least one state that could receive significant outside support: Saudi Arabia. And if it did, proliferation could accelerate throughout the region. Iran and Saudi Arabia have long been geopolitical and ideological rivals. Riyadh would face tremendous pressure to respond in some form to a nuclear-armed Iran, not only to deter Iranian coercion and subversion but also to preserve its sense that Saudi Arabia is the leading nation in the Muslim world. The Saudi government is already pursuing a nuclear power capability, which could be the first step along a slow road to nuclear weapons development. And concerns persist that it might be able to accelerate its progress by exploiting its close ties to Pakistan. During the 1980s, in response to the use of missiles during the Iran-Iraq War and their growing proliferation throughout the region, Saudi Arabia acquired several dozen CSS-2 intermediate-range ballistic missiles from China. The Pakistani government reportedly brokered the deal, and it may have also offered to sell Saudi Arabia nuclear warheads for the CSS-2s, which are not accurate enough to deliver conventional warheads effectively.

There are still rumors that Riyadh and Islamabad have had discussions involving nuclear weapons, nuclear technology, or security guarantees. This "Islamabad option" could develop in one of several different ways. Pakistan could sell operational nuclear weapons and delivery systems to Saudi Arabia, or it could provide the Saudis with the infrastructure, material, and technical support they need to produce nuclear weapons themselves within a matter of years, as opposed to a decade or longer. Not only has Pakistan provided such support in the past, but it is currently building two more heavy-water reactors for plutonium production and a second chemical reprocessing facility to extract plutonium from spent nuclear fuel. In other words, it might accumulate more fissile material than it needs to maintain even a substantially expanded arsenal of its own.

Alternatively, Pakistan might offer an extended deterrent guarantee to Saudi Arabia and deploy nuclear weapons, delivery systems, and troops on Saudi territory, a practice that the United States has employed for decades with its allies. This arrangement could be particularly appealing to both Saudi Arabia and Pakistan. It would allow the Saudis to argue that they are not violating the NPT since they would not be acquiring their own nuclear weapons. And an extended deterrent from Pakistan might be preferable to one from the United States because stationing foreign Muslim forces on Saudi territory would not trigger the kind of popular opposition that would accompany the deployment of U.S. troops. Pakistan, for its part, would gain financial benefits and international clout by deploying nuclear weapons in Saudi Arabia, as well as strategic depth against its chief rival, India.

The Islamabad option raises a host of difficult issues, perhaps the most worrisome being how India would respond. Would it target Pakistan's weapons in Saudi Arabia with its own conventional or nuclear weapons? How would this expanded nuclear competition influence stability during a crisis in either the Middle East or South Asia? Regardless of India's reaction, any decision by the Saudi government to seek out nuclear weapons, by whatever means, would be highly destabilizing. It would increase the incentives of other nations in the Middle East to pursue nuclear weapons of their own. And it could increase their ability to do so by eroding the remaining barriers to nuclear proliferation: each additional state that acquires nuclear weapons weakens the nonproliferation regime, even if its particular method of acquisition only circumvents, rather than violates, the NPT.

N-PLAYER COMPETITION

Were Saudi Arabia to acquire nuclear weapons, the Middle East would count three nuclear-armed states, and perhaps more before long. It is unclear how such an n-player competition would unfold because most analyses of nuclear deterrence are based on the U.S.-Soviet rivalry during the Cold War. It seems likely, however, that the interaction among three or more nuclear-armed powers would be more prone to miscalculation and escalation than a bipolar competition. During the Cold War, the United States and the Soviet Union only needed to concern themselves with an attack from the other. Multipolar systems are generally considered to be less stable than bipolar systems because coalitions can shift quickly, upsetting the balance of power and creating incentives for an attack.

More important, emerging nuclear powers in the Middle East might not take the costly steps necessary to preserve regional stability and avoid a nuclear exchange. For nuclear-armed states, the bedrock of deterrence is the knowledge that each side has a secure second-strike capability, so that no state can launch an attack with the expectation that it can wipe out its opponents' forces and avoid a devastating retaliation. However, emerging nuclear powers might not invest in expensive but survivable capabilities such as hardened missile silos or submarine-based nuclear forces. Given this likely vulnerability, the close proximity of states in the Middle East, and the very short flight times of ballistic missiles in the region, any new nuclear powers might be compelled to "launch on warning" of an attack or even, during a crisis, to use their nuclear forces preemptively. Their governments might also delegate launch authority to lower-level commanders, heightening the possibility of miscalculation and escalation. Moreover, if early warning systems were not integrated into robust command-and-control systems, the risk of an unauthorized or accidental launch would increase further still. And without sophisticated early warning systems, a nuclear attack might be unattributable or attributed incorrectly. That is, assuming that the leadership of a targeted state survived a first strike, it might not be able to accurately determine which nation was responsible. And this uncertainty, when combined with the pressure to respond quickly, would create a significant risk that it would retaliate against the wrong party, potentially triggering a regional nuclear war.

Most existing nuclear powers have taken steps to protect their nuclear weapons from unauthorized use: from closely screening key personnel to developing technical safety measures, such as permissive action links, which require special codes before the weapons can be armed. Yet there is no guarantee that emerging nuclear powers would be willing or able to implement these measures, creating a significant risk that their governments might lose control over the weapons or nuclear material and that nonstate actors could gain access to these items. Some states might seek to mitigate threats to their nuclear arsenals; for instance, they might hide their weapons. In that case, however, a single intelligence compromise could leave their weapons vulnerable to attack or theft.

Meanwhile, states outside the Middle East could also be a source of instability. Throughout the Cold War, the United States and the Soviet Union were engaged in a nuclear arms race that other nations were essentially powerless to influence. In a multipolar nuclear Middle East, other nuclear powers and states with advanced military technology could influence -- for good or ill -- the military competition within the region by selling or transferring technologies that most local actors lack today: solid-fuel rocket motors, enhanced missile-guidance systems, warhead miniaturization technology, early warning systems, air and missile defenses. Such transfers could stabilize a fragile nuclear balance if the emerging nuclear powers acquired more survivable arsenals as a result. But they could also be highly destabilizing. If, for example, an outside power sought to curry favor with a potential client state or gain influence with a prospective ally, it might share with that state the technology it needed to enhance the accuracy of its missiles and thereby increase its ability to launch a disarming first strike against any adversary. The ability of existing nuclear powers and other technically advanced military states to shape the emerging nuclear competition in the Middle East could lead to a new Great Game, with unpredictable consequences.

INCREDIBLE DETERRENTS

If Iran did acquire nuclear weapons, would a containment strategy preserve stability in the Middle East? Some analysts, including Lindsay and Takeyh, argue that although Iran can be aggressive at times, it also regulates its behavior to avoid provoking retaliation. Since the regime is sensitive to costs, the logic goes, it recognizes the dangers of escalation; hence, containment would work. Other analysts argue that Iran's antagonism toward the United States and Israel is so strong and so central to its leaders' legitimacy that Tehran will become more hostile once it has a nuclear arsenal, regardless of the consequences.

The truth probably lies somewhere in between. Tehran may not be irrationally aggressive, but its leadership structure and decision-making are opaque. Its rhetoric toward the United States, Israel, and the Arab nations is often inflammatory. And its hostile behavior -- including its support for proxies such as Hezbollah, its efforts to subvert its neighbors, and its provocative naval maneuvers in the Persian Gulf -- could easily trigger a crisis. In short, it is unclear how a nuclear-armed Iran would weigh the costs, benefits, and risks of brinkmanship and escalation and therefore how easily it could be deterred from attacking the United States' interests or partners in the Middle East.

One of the most important elements of a U.S. containment strategy would be extended deterrence, that is, discouraging Iran from attacking states in the Middle East. Over the past several years, it has become popular in policy circles to think that containing a nuclear-armed Iran, stabilizing relations between Iran and Israel, and preventing additional proliferation will require expanding U.S. security commitments to several U.S. allies and partners in the Middle East. In July 2009, for example, Secretary of State Hillary Clinton suggested that the United States would extend "a defense umbrella over the region" in order to prevent Iran from continuing to pursue nuclear weapons, to deter Iranian aggression if Tehran does acquire nuclear weapons, and also, presumably, to dissuade U.S. allies and partners from pursuing nuclear weapons as well.

At first blush, a policy of extended deterrence might appear to be a sensible and effective approach. It played an important role in deterring a Soviet attack on the West and limiting nuclear proliferation during the Cold War. Seeking a nuclear-armed patron is an attractive option for states that are insecure but unwilling or unable to accept the burdens and risks of pursuing their own nuclear programs. In addition, the United States already has a strong foundation of alliances and security partnerships, including its long-standing "special relationship" with Israel; its close ties to Bahrain, Egypt, Iraq, Jordan, Saudi Arabia, and the United Arab Emirates; and Turkey's membership in NATO. And it has unique capabilities that states in the region will almost certainly want to see used on their behalf, including ballistic missile defenses (which could be used to counter Iran's principal delivery methods) and early warning systems (which are particularly important given the short flight times of any missiles that might be launched from Iran toward its neighbors).

Yet a strategy rooted in extended deterrence could prove far more challenging and far less effective than most analysts and policymakers recognize. Its proponents tend to draw heavily on the experience of the Cold War, but this parallel oversimplifies the problems that the United States would face if nuclear proliferation occurred in the Middle East. Throughout the U.S.-Soviet rivalry, the United States and the allies under its nuclear umbrella were not only aligned against a single overriding threat; they also had few serious security challenges among themselves, particularly as the rivalry between France and Germany dissipated in the 1950s and 1960s. Today, most Middle Eastern states view Iran as a threat, but their own relations remain tense, and in some cases even hostile. These cross-cutting rivalries could complicate U.S. efforts to establish an effective extended deterrence regime in the region, particularly if Washington pledged to defend both Israel and several Arab states.

During the Cold War, the United States deployed several hundred thousand troops to Western Europe, to democratic nations that faced an authoritarian Soviet Union threatening to dominate all of Europe. The U.S.-Soviet competition was a struggle for global dominance, U.S. allies were culturally and politically far more similar to the United States than its current security partners in the Middle East, and both the United States' treaty commitments and its forward-based forces were clear indicators of its willingness to defend its allies. Nevertheless, doubts persisted about whether the United States would be willing to use nuclear weapons against the Soviet Union to stave off a military defeat in Europe. And if the United States' allies then were never truly convinced that it would risk New York to save Bonn, London, or Paris, then why would U.S. allies in the Middle East today believe that it would risk New York to defend Cairo, Dubai, or Riyadh once Tehran acquired the means to target the U.S. homeland with nuclear weapons? Tehran could have such a capability shortly after developing nuclear weapons if it relied on unconventional means of delivery, such as transport inside a cargo ship rather than intercontinental ballistic missiles.

Meanwhile, the U.S. Congress might be reluctant to formally endorse a pledge to defend Arab nations, in particular given the resentment toward the United States that exists in many of these countries. Even informal public guarantees could generate significant opposition in Congress. And private commitments are unlikely to be effective, because unlike with public declarations, Washington would not be putting its reputation on the line. Another difference between the Soviet Union and a nuclear-armed Iran is that in most instances with Iran, the United States would not have the option of using significant forward-based forces as a tripwire and so would lack a way to signal its willingness to retaliate after any attack against its partners in the Middle East. Many of those governments would not welcome the presence of U.S. troops because they are reluctant to be perceived by their domestic audiences as U.S. protectorates unable to defend themselves.

ACCEPTING THE UNACCEPTABLE

Other serious questions surround the credibility of a U.S. extended deterrence regime. First and foremost, Washington would be issuing a guarantee despite having failed to halt Iran's nuclear program -- after three successive U.S. presidents declared that a nuclear-armed Iran would be a major threat to U.S. security and to stability in the Middle East. Managing the balance of terror during the Cold War may have required "thinking the unthinkable," but for many, the United States' failure to halt Iran's pursuit of a nuclear weapons capability would be "accepting the unacceptable." If the United States cannot prevent a conventionally armed Iran from acquiring nuclear weapons, its partners in the Middle East will almost certainly question its willingness to stand up to a nuclear-armed Iran.

Moreover, if the United States fulfills its obligations under the New Strategic Arms Reduction Treaty and the plans in the Nuclear Posture Review to further reduce its nuclear force and refrain from developing any new warheads, its nuclear arsenal will be shrinking just as its security commitments are expanding substantially. The United States has traditionally adapted the size and the composition of its nuclear arsenal according to the Soviet Union's (and later Russia's) force. Now, however, it must be able to deter attacks against its territory by several countries: Russia, still, as well as China, North Korea, and perhaps soon Iran. And it must also deter attacks against the many states under its nuclear umbrella, including the more than two dozen NATO members in Europe and its allies in Asia, such as Australia, Japan, and South Korea. As the U.S. arsenal decreases, Washington will have fewer weapons to support these commitments, which will raise questions about its ability and its willingness to defend its allies and its partners if they are threatened by a nuclear-armed Iran. Because the United States has thus far chosen not to design a new generation of nuclear weapons, its remaining inventory will consist primarily of high-yield warheads designed to target large cities and civilian populations. This may create the perception among both its allies and its adversaries that the United States is self-deterred -- that it will not be willing to employ nuclear weapons in retaliation for an attack on one of its partners because of the enormous collateral damage and high number of civilian casualties that would result.

The United States does have significant ballistic missile defense capabilities, which could strengthen extended deterrence by countering Iran's most likely nuclear delivery systems. Yet when other requirements are taken into account, in particular the need to protect the United States' allies and bases in Europe and Asia, it is unlikely that sufficient ground- and sea-based systems will be available to defend against a threat to U.S. partners in the Middle East. This problem will only become worse as Tehran's ballistic missile inventory grows over time. Iran will eventually be able to overwhelm U.S. missile defenses with salvos of conventionally armed missiles. Because existing defense systems cannot discriminate between nuclear and nonnuclear warheads, such attacks could exhaust the missile defenses of the United States and its allies, leaving those countries vulnerable to follow-on attacks with nuclear weapons. Missile defense systems cost far more than offensive ballistic missiles, and so building more of the former to keep pace with Iran as it builds more of the latter would place the United States at the wrong end of the cost equation -- at a time when fewer resources are likely to be available to the Pentagon.

The danger posed by Iran's ballistic missiles creates further doubts about the credibility of any U.S. security guarantees. Would the United States be willing to exhaust its missile defenses to protect Egypt, Iraq, or Saudi Arabia from an Iranian missile attack, even though this would leave Israel vulnerable to a follow-on strike? Would the countries of the Middle East trust the United States to use all of its missile interceptors to defend them, knowing that it would be extremely reluctant to leave Israel, its closest ally in the region, unprotected? Would it rush additional sea-based missile defenses to the region during a crisis, aware that doing so might trigger a preemptive attack by Iran (which may choose to strike before its adversaries become less vulnerable) or a U.S. ally (which might assume that the United States will help intercept an Iranian retaliatory strike)?

Finally, the United States would confront a fundamental dilemma as it attempted to contain a nuclear-armed Iran: the Iranian actions that are the easiest to deter, namely, a deliberate conventional or nuclear attack, are the least likely forms of Iranian aggression, whereas Iran's most likely forms of aggression, in particular support for terrorism and subversion, are the most difficult to deter. Middle Eastern states take these lower-level threats very seriously, but because such threats are difficult to attribute and inflict less damage than a nuclear or a conventional attack, any promise the United States makes to retaliate forcefully, with nuclear weapons or not, is unlikely to be viewed as credible, either in Tehran or among U.S. allies.

In sum, any U.S. effort to implement an extended deterrence regime in the Middle East in order to contain a nuclear Iran and stem proliferation in the region would face very serious challenges. Given the magnitude of those challenges, the United States must redouble its efforts to prevent Iran from acquiring nuclear weapons while also taking steps that will bolster its credibility if containment becomes necessary because Iran has acquired nuclear weapons.

WHAT TO DO?

Not surprisingly, when it comes to addressing the dangers posed by Iran's nuclear program, there simply are no good options. Thus far, diplomacy and economic sanctions only seem to have hardened Iran's resolve to develop a nuclear capability. Although clandestine efforts to disrupt Iran's nuclear program might delay its progress, they are unlikely to prevent Iran from acquiring nuclear weapons. An Israeli strike against Iran's nuclear infrastructure might set the program back but, given Israel's limited long-range strike capability, only for a short period of time. Even though the United States could bring more capabilities to bear, and a U.S. military campaign against Iran's nuclear program might stand a greater chance of retarding its progress, the operational military challenges would be daunting. Moreover, an attack could backfire: it might enhance popular support for a regime that has grown increasingly unpopular at home, further strengthen Iran's determination to go nuclear, and trigger a costly retaliation against the United States and U.S. allies in the Middle East. Yet the alternative -- trying to deter a nuclear-armed Iran from aggressive behavior against the United States, its allies, or its interests in the region -- would almost certainly be prohibitively expensive, difficult to implement successfully, and challenging to sustain over time.

What, then, should the United States do? At present, the best strategy is a three-track approach that brings diplomacy and sanctions, clandestine action, and the threat of military force into alignment. First, the United States should continue to apply diplomatic and economic pressure on Iran, both to raise the costs of Iran's pursuing a nuclear weapons capability and to further isolate the country from the international community, its leaders from the Iranian people, and hard-liners within the government from their more pragmatic colleagues. Although these policies have enjoyed only limited success to this point, given the regime's opaque politics, it is possible that they are generating greater costs in Tehran than is apparent. Moreover, a durable resolution to this dispute may rest on the possibility, however small, that a significant portion of the Iranian public, as well as the Iranian elite, will conclude that the game is not worth the candle. If the United States and the international community can delay Iran's acquisition of nuclear weapons, the cumulative effect of sanctions and isolation -- and Tehran's knowledge that Iran will remain a pariah state until it abandons its nuclear ambitions -- could have that effect. At a minimum, continuing to employ diplomatic and economic tools would demonstrate that the United States prefers a nonmilitary approach to the problem, which could help dampen criticism if more forceful measures ever proved necessary.

Second, recent press reports suggest that several states might be trying to sabotage Iran's nuclear program. If so, and if they are successful, the moves would buy additional time for diplomacy to work, for effective military options to be developed, and for steps to be taken that could reduce U.S. vulnerability to any Iranian retaliation. Sabotage could be particularly important if Tehran chooses to pursue a "nuclear breakout" strategy: deferring weaponization until it has enough fissile material for at least a handful of warheads. In fact, this may be Iran's most likely strategy: not only would it discourage a preventive attack by exploiting the ambiguity that currently surrounds Iran's nuclear program; it would also provide Iran with a more robust deterrent when it crossed the nuclear threshold. But because Iran would need a significant quantity of fissile material before it could build and test its arsenal, hindering its ability to produce enriched uranium would present it with a difficult dilemma: build a very small number of weapons quickly even though they might be vulnerable to attack or wait until a larger inventory can be produced at once. If Tehran chose the latter option, the United States could gain considerably more time to stop Iran's progress or prepare for a nuclear-armed Iran.

Third, the United States should bolster its military capabilities in and around the Persian Gulf and deploy there additional B-2 stealth bombers; stockpiles of precision-guided munitions; electronic warfare systems; undersea strike assets, such as guided missile submarines; sea-based missile defense platforms; and possibly a second aircraft carrier strike group. Along with the U.S. forces already stationed in the region, these added capabilities would strengthen the Obama administration's current diplomatic efforts and expand Washington's options for countering the Iranian nuclear program if diplomacy fails. Extra forces would complement diplomacy with added coercive pressure. To date, public statements by senior U.S. military and civilian officials, including Secretary of Defense Robert Gates and Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, have come very close to taking the military option off the table, citing the difficulties of an attack and the dangers of retaliation. If Iran's leaders conclude that the United States cannot or will not use force against their nuclear program, they will have fewer incentives to forgo nuclear weapons.

At the same time, a more robust U.S. military posture would demonstrate that the benefits Iran might have anticipated from its nuclear weapons program -- driving the United States out of the region and weakening its local alliances -- are unlikely to materialize. It would also go some way toward reassuring U.S. allies and security partners that Washington is committed to their defense. Even if the Obama administration concludes that a nuclear-armed Iran can be deterred and additional proliferation in the Middle East can be avoided, or if efforts to prevent Iran from crossing the nuclear threshold fail, the United States must still take steps now to mitigate the credibility problems that will almost certainly arise if Iran does acquire nuclear weapons and so containment becomes necessary. Finally, additional U.S. forces would place the United States in a better position to execute a military strike on short notice if Washington determined that an attack could set back Iran's nuclear program for at least several years, if not more, and that the potential costs of an Iranian retaliation were tolerable.

Although finding a peaceful way to preclude Iran from getting nuclear weapons is obviously desirable, Washington will likely have to decide between two unattractive options: pursuing a military strike to prevent Iran from going nuclear or implementing a containment strategy to live with a nuclear Iran. The resort to force is always risky, and it would be particularly so in this case because a substantial number of U.S. troops are deployed near Iran. Whether force should be used will depend on the answers to three difficult questions: How close is Iran to achieving a nuclear weapons capability? Would an attack be effective? How might Iran retaliate, and what costs would the United States and its allies and partners suffer as a result? The risks of war must be weighed against the likelihood that containment could preserve regional stability and avert further proliferation, the demands of implementing and sustaining a containment strategy, and the inevitable reduction in the United States' ability to defend vital interests elsewhere.

The consequences of a nuclear-armed Iran are grave, and the challenges of a containment strategy rooted in extended deterrence are hardly trivial. The military option should not be dismissed because of the appealing but flawed notion that containment is a relatively easy or low-risk solution to a very difficult problem. Instead, containment could require a far larger military presence than the United States has traditionally maintained in the Middle East, particularly in the form air and naval forces, as well as major investments in expensive capabilities, such as missile defenses, a modernized nuclear arsenal with more low-yield weapons, agile diplomacy to create and preserve cohesion among diverse allies, and far tougher economic sanctions than have heretofore been possible. Understanding and addressing these requirements will be crucial if the United States decides to attempt to contain a nuclear-armed Iran, either because it assesses the costs and difficulties of prevention as too high or because Iran crosses the nuclear threshold faster than expected and no better options remain.