Iranian President Hassan Rouhani in New York, September 2014.
Adrees Latif / Courtesy Reuters

In the recently extended negotiations over the future of Iran’s nuclear program, the main sticking point has always been the number of centrifuges that Tehran will be allowed to keep for enriching uranium. This number is important because the more working centrifuges Iran has, the faster it could achieve a nuclear breakout. According to standard estimates, Iran’s current inventory of approximately 10,000 operational centrifuges could allow it to amass enough weapons-grade uranium for a single bomb in just a few months. The Barack Obama administration believes that it can convince Iran to roll back that timeline far enough to defuse the current crisis, allowing both sides to develop a more normal relationship. 

Critics of the negotiations have argued that the United States and other P5+1 (the five permanent members of the UN Security Council plus Germany) have a misplaced focus on the number of centrifuges at Iran’s known nuclear facilities. According to them, the “breakout” scenario that has been keeping the negotiators up at night is not nearly as dangerous as the alternative scenario of an Iranian nuclear “sneak-out.” An Iran that had decided to sneak out rather than break out would play by the rules at closely monitored enrichment plants and other known facilities, while secretly building a bomb elsewhere. Thus, to be effective, a comprehensive nuclear agreement with Iran would have to flood Iran with international inspectors—something no self-respecting government in Tehran could ever accept. In short, the higher the chances of the sneak-out scenario, the lower the chances of a halfway decent settlement with Iran.

Washington and its partners certainly need to be on guard for all sorts of contingencies. Although it is debatable whether or not Iran really wants the bomb, the country has a demonstrated penchant for secret nuclear activities. It acknowledged the existence of its two enrichment facilities, for example, only after outside intelligence agencies discovered the first in 2002 and the second in 2009. Even today, when international investigators demand access to suspect sites or key individuals, it often seems that Tehran’s first instinct is to stonewall.      

Although the chances of an Iranian sneak-out attempt are relatively great, however, its odds of success are extremely low. With the world’s spy agencies devoting huge resources to tracking events inside Iran, any serious attempt at cheating under a new nuclear deal would probably get caught. If Tehran somehow did manage to cheat without notice, its secret program would nonetheless advance slowly. Moreover, even in the unlikely eventuality of a highly efficient secret effort, Iran would still fall short of a bona fide nuclear weapons arsenal. The major powers, then, are right to focus on getting an agreement that limits Iran’s genuine breakout potential, not its highly questionable sneak-out potential. 

Iran has often tried to build advanced nuclear capabilities in secret. But time and again, it has gotten caught in the act. Both of Iran’s uranium enrichment plants, for example, were discovered at early stages of construction. Pessimists point to this past cheating as evidence of Tehran’s untrustworthiness, but that same track record also demonstrates that the United States and its partners cannot be easily duped. Moreover, a diplomatic accord with Iran would not stop Western intelligence agencies from looking out for possible Iranian malfeasance. And the more access the International Atomic Energy Agency’s inspectors have to Iran’s nuclear program, the easier it will be to detect any covert activities. 

Even if Iran were to cheat and somehow elude detection for more than a few months, it would not be able to progress nearly as far toward the bomb as it could if it were using its existing facilities. Any state’s nuclear timeline naturally becomes much longer if it has to build an entirely new program, and longer still if it has to do so in total secrecy. 

The drawbacks of overestimating how far countries may get by cheating are made clear by the case of North Korea. The Bill Clinton administration’s 1994 deal to halt Pyongyang’s plutonium stockpiling, known as the Agreed Framework, is often criticized because it did not prevent North Korea from secretly trying to enrich uranium on the side. But the George W. Bush administration was wrong to rip up the agreement, even after it discovered cheating. This is because Pyongyang’s secret uranium enrichment effort had progressed slowly and was far from capable of producing enough fissile material for a bomb, in contrast to its frozen but still functional plutonium production line. Indeed, it was with evident relief that the regime of Kim Jong Il started up its plutonium production facilities again in the wake of U.S. accusations against its uranium enrichment work. The regime’s nuclear tests in 2006 and 2009 made use of plutonium from known facilities—not enriched uranium from secret ones. Even today, some two decades after North Korea launched its secret enrichment program, it remains unclear if North Korea is capable of producing a significant quantity of highly enriched uranium. 

The ultimate fear is that an Iranian sneak-out could result in not just a secret stockpile of weapons-grade uranium but also functional nuclear bombs. Yet this scenario is even more far-fetched than the proposition that Iran might be able to mount a huge parallel nuclear program without anyone noticing.

The vast majority of nuclear weapons states have conducted an explosive test prior to the construction of operational nuclear weapons. Typically, this first test has preceded the birth of a genuine military arsenal by several months or more. Such tests may not be strictly necessary from an engineering point of view, but they are almost always necessary for political reasons. And thanks to advances in seismic monitoring technology, nuclear tests can’t be concealed anymore. If Iran were to go for the bomb, then, its nuclear test would open a clear window for a preemptive strike by the United States.                                        

Skeptics of this argument may point to the unique case of Israel, which was able to develop an untested but fearsome nuclear arsenal in the 1960s and 1970s. But as the political scientist Matthew Gratias and I have detailed, Israel’s achievement depended on several key factors that are not present in the Iranian case. Israel was able to keep its march to nuclear status under wraps because it did not face an existing nuclear threat in the region, because the United States was complicit with its decision to keep quiet, because it had a highly disciplined state apparatus that could keep a secret, and because the country’s politicians trusted its scientists. Iran, by contrast, faces hostile nuclear powers in its own neighborhood and beyond, and neither Israel nor the United States would remain silent in the face of mounting evidence of an Iranian nuclear weapons capability. Moreover, the Iranian state remains riddled with competing political factions, and the country’s leaders have demonstrated little trust in their scientific and technical professionals.

Iran’s propensity to test its developing strategic weapons capabilities is reflected in the history of its ballistic missile program. Iran has fired test missiles dozens of times for all sorts of reasons, and many of those tests have flopped, giving the world a clear picture of its growing but still limited capabilities. One can expect the same in the nuclear field. If Iran sprinted toward the bomb, the world would know before it reached the finish line. 

The scenario of a devastating Iranian sneak-out is nothing more than a fanciful hypothetical. Washington and its partners should not let the fear of such a low-probability event divert their attention from what remains an attainable and worthy goal: a comprehensive agreement that brings about a substantial cut in Iran’s actual uranium enrichment capabilities while showing due respect for Iran’s legitimate desires for economic development and national scientific achievement.