Iran’s New Nuclear Threat

In April, the simmering war in the Middle East nearly took a nuclear turn when Tehran launched more than 300 missiles and suicide drones at Israel in retaliation for its strike on the Iranian consulate in Syria. This was Iran’s first direct attack on Israel, and international inspectors stayed away from Iran’s nuclear facilities for fear of a retaliatory response. As the world waited, the Iranian military commander in charge of defending the Islamic Republic’s nuclear sites publicly warned that if Israel attacked the sites, Tehran could revise its nuclear doctrine. This was a thinly veiled threat that Iran might build nuclear weapons in response.

Tehran has long used threats of nuclear expansion to reduce international pressure. But the military commander’s statement highlights a new and dangerous evolution in Iran’s strategy, which is to use the country’s enhanced ability to build a nuclear weapon as a deterrent. Most evidence suggests that Iran is not developing nuclear weapons and Supreme Leader Ali Khamenei has so far put off building them because he sees the risks as outweighing the rewards. But in recent years, Iran has gradually acquired many of the key capabilities necessary to build a nuclear weapon, becoming a so-called threshold state. Iran can now, in a matter of days, produce enough highly enriched uranium to make a bomb. By highlighting its bomb-making potential and responding to specific provocations by threatening to take the final steps to build nuclear weapons, Tehran hopes it can prevent international sanctions and a strike against its nuclear program.

But this strategy is not risk free, and Tehran remains sensitive to the potential security costs of developing nuclear weapons. Stopping Iran from producing a bomb will not be easy, but reducing Tehran’s nuclear capabilities will be even harder. Washington should make Iran a priority and bring U.S. diplomatic and economic might to bear, to prevent the catastrophe of Iran as a permanent threshold state, or one armed with nuclear weapons.

RATTLING SABERS

One of the earliest indications that Iran was seeking to use its nuclear threshold capacity as a deterrent appeared in 2023, after France, Germany, and the United Kingdom threatened to reimpose UN Security Council sanctions on Iran if it enriched uranium to weapons grade or transferred missiles to Russia. In response, Tehran threatened to withdraw from the Nuclear Nonproliferation Treaty. That would have removed the most important legal barrier between Iran and the bomb and likely eliminated international monitoring of its nuclear program, meaning that the world would have no way of knowing whether Iran was building a weapon. These threats seem to have had the desired effect. So far, Iran has not enriched to the 90 percent that is typically considered weapons-grade uranium, and Europe has not reimposed sanctions. But with the crisis unresolved, the threats are likely to resurface.

Iran’s strategy of warning that it will build a bomb has become more prominent, public, and explicit in the wake of October 7 and the ensuing war in Gaza. Throughout the conflict, Iran has mounted a steady drumbeat of attacks on Israel, U.S. forces, and international shipping via its surrogate groups across the region. Iran’s nuclear program has played a role in Iran’s management of the crisis, too, as Tehran has relied on a combination of technical signaling and rhetoric to bolster the credibility of its threshold deterrent and manage escalation risks. That Iran’s leaders have not kept the nuclear program out of the spotlight is a sign that they view their threshold capability as more of an asset than a liability. For example, last December Iran reverted the configuration of its advanced centrifuges to a setup that in early 2023 had produced small amounts of 84 percent enriched material—a hair’s breadth away from the 90 percent needed for nuclear weapons. Tehran knew inspectors would see and report the December change, which strongly suggests its leaders wanted to communicate that the possibility of producing weapons-grade uranium was back on the table.

Iranian officials have also ramped up their commentary about the country’s ability to build nuclear weapons and the conditions under which they might do so. In January, the head of Iran’s nuclear program, Mohammed Eslami, repeated the long-standing Iranian position that weapons of mass destruction have “never been part of [its] security and defense doctrine” but added that Iran’s nuclear latency—its inherent capacity to build nuclear weapons—provided a deterrent. “It is not about the lack of capability,” he declared in a televised interview. “I think we have achieved such deterrence . . . . We should not underrate our current achievements, thinking that we are not there yet.” The Iranian government then circulated Eslami’s statement on social media. The next month, his predecessor and one of the key negotiators of the 2015 nuclear deal, Ali Akbar Salehi, elaborated on Eslami’s point. When asked whether Iran can build a nuclear bomb, Salehi replied that Iran has crossed “all the scientific and technical nuclear thresholds.” Using the example of manufacturing a car, he continued: “What does it take to make a car? You need a chassis, an engine, a wheel, a gearbox . . . . If you are asking me if we [have] built the gearbox and the engine, my answer is yes.”

Iran can now, in a matter of days, produce enough highly enriched uranium to make a bomb.

Iranian newspapers, parliamentarians, nuclear scientists, and other officials joined in, with many noting that Iran might even build a bomb. In addition to the threats made by the senior military official during the tit-for-tat attacks between Iran and Israel in April, Kamal Kharrazi, the Supreme Leader’s foreign policy adviser, stated in early May that “should Iran’s existence be threatened, there will be no choice but to change our military doctrine.” He repeated the threat days later, and former Deputy Foreign Minister Abbas Araghchi made similar comments toward the end of the month. Iran’s mission to the UN parroted the Ministry of Foreign Affairs’ position that Iran’s nuclear doctrine had not changed, but added a caveat. Following an attack on Iran’s nuclear facilities, the mission threatened, Iran might terminate the legal mechanism that provides international inspectors access to its nuclear facilities and conceal from the world what is going on inside.

It is difficult to know whether this is a coordinated, top-down regime messaging strategy or a bottom-up phenomenon. As Tehran’s capabilities stand today, it could not immediately make good on threats to build nuclear weapons. Although it can quickly produce the material for a bomb, building a device would take many months. Even so, it is clear that senior leaders want to leverage Iran’s nuclear program as a deterrent. The fact that Supreme Leader Khamenei—who sets the terms of acceptable public debate within Iran—allows these statements to be issued is telling. It suggests that he finds them useful for domestic political reasons, foreign policy purposes, or both.

There is a risk, however, that the continued talk of Iran’s ability to build nuclear weapons becomes a self-fulfilling prophecy. Iranian officials who favor building a nuclear arsenal may see this rhetoric as an opening to press their case for a bomb or to nudge closer to the threshold. They could perhaps interpret Khamenei’s silence on these public statements as a sign of his implicit support. This could become dangerous because Iran’s decision-making circles have become narrower and more hard line, with fewer moderate voices to push back against arguments for developing nuclear weapons. Advocates for nuclear weapons could feel emboldened to push their case.

DON’T DO IT!

As the United States and its allies continue to search for a diplomatic solution to the Iranian nuclear challenge, they must manage its threats and prevent it from crossing the threshold. There is space for progress because, for Iran’s warnings to work, the United States and its allies must believe that Iran will refrain from building nuclear weapons if the country’s specified redlines are respected. These redlines appear to be the “snap back” of UN sanctions, meaning the reimposition of UN Security Council resolutions removed as part of the 2015 nuclear deal, or a military strike on Iran’s nuclear program. The more Iran impedes international monitoring of its program, however, the harder it is to guarantee that its redlines will be respected, and the likelier a military strike on Iran’s program based on mistaken assumptions becomes.

If Tehran wants to avoid that outcome, then granting greater access can help provide that reassurance, a point that countries including France, Germany, the United Kingdom, and the United States should reinforce to Iran. For example, Tehran could allow inspectors regular access to its centrifuge production sites and permit the use of cameras and other devices to monitor Iran’s nuclear program in real time when inspectors are not there. The United States and its allies can also raise the diplomatic costs of Iran’s bomb-making rhetoric. At the recent meeting of the International Atomic Energy Agency, France, Germany, the United Kingdom, and the United States called out these threats alongside Iran’s continuing nuclear expansion and lack of transparency, and codified those condemnations in a resolution. Washington should work to enlist more countries—including China and others that hold influence with Tehran—to press these concerns privately and publicly by pointing out that Iran’s boasts that it has the capacity to build the bomb contradicts its claims that its program is entirely peaceful.

There is a risk that the continued talk of Iran’s ability to build nuclear weapons becomes a self-fulfilling prophecy.

Even if Israel and the United States, as well as France, Germany and the United Kingdom, do not cross Iranian redlines, Tehran could still be tempted to move closer to a bomb. It may do so by accumulating enriched material just below 90 percent to avoid triggering an international response, or by covertly conducting the research and development required for packaging that material into an explosive device. To prevent these actions, Washington and its allies must ensure that such steps are quickly detected and result in consequences for Iran—and that Tehran knows it. This requires strengthening intelligence capabilities, supporting the International Atomic Energy Agency’s investigations, and having coordinated plans in place to respond to Iranian nuclear provocations in a proportionate manner. To bolster this strategy, Washington should consider releasing intelligence about any current undeclared Iranian nuclear activities. Outing such activities in the past—for example, on Iran’s covert enrichment activities in 2002 and 2009—helped build international pressure on Iran and put it on the defensive. That exposure can also undermine Tehran’s confidence that it can build a bomb undetected. In addition, the United States should make clear to Tehran that crossing the nuclear threshold would lead to a greater U.S. military presence in the region and stronger security arrangements between Washington and Gulf states, hindering Iran’s long-term goal of ejecting the United States from the Middle East.

Getting a deal that can meaningfully roll back Iran’s program will be more challenging. Tehran’s goal will likely be to maintain its threshold status, and the clock is ticking. October 2025 is the de facto deadline for the conclusion of nuclear talks with Iran, after which the ability of the remaining parties to the deal—China, France, Germany, Russia, and the United Kingdom—to reimpose international sanctions via the 2015 nuclear deal will expire, and Iran’s nuclear program will be removed from the UN Security Council’s agenda. For Tehran, reaching this date holds the promise of fulfilling its twin goals of dismantling the UN sanctions architecture and retaining its nuclear threshold capability. This is a scenario that the United States and its allies want to avoid, given that Russia and China would veto any attempts to create new UN sanctions. Although unilateral sanctions imposed by the United States and Europe would remain in place, and Russia and China may decide to ignore sanctions imposed via the snap-back mechanism, Tehran loathes the stigma attached to international censure and knows that it will never be fully in the clear as long as its nuclear file sits before the Security Council.

This sows the seeds for a potential crisis in 2025, which could result in a war, a nuclear-armed Iran, or Iran as a permanent nuclear threshold state. There can be no going back to the 2015 nuclear deal given Iran’s technical advances, and the chances of a new deal are slim. But given the potential consequences of failure, the United States should not give up. To improve its chances, Washington, working with its allies, should decide on its desired parameters for a new deal and communicate those—as well as its preference for a diplomatic solution—to Iran as soon as possible. In tandem, the United States and Europe should tackle the delicate task of rebuilding leverage by gradually increasing diplomatic and economic pressure on Iran between now and October 2025, without triggering Iranian nuclear moves that would doom the prospects of securing a diplomatic agreement. That will not be easy, nor will it be without risk. But it is certainly preferable to the alternatives.