Bombing Iran's Nuclear Program: Implications of Preventive Action

On March 19, The Washington Institute held a virtual Policy Forum with Dana Stroul, Richard Nephew, Michael Eisenstadt, and Holly Dagres. Stroul is the Institute’s Kassen Senior Fellow and director of research. Nephew is the Institute’s Bernstein Adjunct Fellow and former deputy special envoy for Iran at the State Department. Eisenstadt is the Institute’s Kahn Senior Fellow, director of its Military and Security Studies Program, and author of its new paper “Attacking Iran’s Nuclear Program: The Complex Calculus of Preventive Action.” Dagres is the Libitzky Family Senior Fellow in the Institute’s Viterbi Program on Iran and U.S. Policy. The following is a rapporteur’s summary of their remarks.

Dana Stroul

The Trump administration’s first few weeks in office have already seen significant developments in U.S. policy toward Iran, including an executive order reconstituting the “maximum pressure” campaign, public statements indicating both preparedness to use military force and a desire to negotiate, and an exchange of letters between President Trump and Supreme Leader Ali Khamenei. Washington believes Tehran has suffered substantial setbacks during the war in Gaza; indeed, the regime may be more exposed than ever due to the collapse of its regional threat network and successive rounds of military strikes on Iranian soil, which damaged its strategic air defenses and other vital assets. In light of these vulnerabilities, many U.S. and Israeli officials conclude that the clock is now ticking on wider military action against Iran.

Regarding the regime’s nuclear status, the 2015 Joint Comprehensive Plan of Action (JCPOA) imposed constraints on Iran’s nuclear program in return for some sanctions relief. Since President Trump’s 2018 withdrawal from that agreement, however, Tehran has continued gradually advancing the program and is now much closer to crossing the nuclear weapons threshold.

Richard Nephew

Several technical developments over the past seven years have increased the risk that Iran will be able to break out with a nuclear weapon quickly if it so chooses. Last year, former secretary of state Antony Blinken indicated that the regime could produce enough high-enriched uranium (HEU) for one bomb within six to seven days, and this timeline may be even shorter today. The most salient factors in this advancement are Iran’s growing stockpile of 60 percent enriched uranium (only a stone’s throw from weapons-grade uranium in terms of additional enrichment time) and its deployment of advanced centrifuges that are three times as efficient as its original model. 

The good news is that Iran is still allowing officials from the International Atomic Energy Agency (IAEA) to access the program, giving the international community some ability to identify if and when the regime jumps to producing 90 percent uranium (i.e., weapons-grade). The bad news is that Iran is now so close to breakout that the margins for responding to such a decision and preventing actual weaponization are exceedingly thin. Moreover, nothing is keeping Iran from moving materials to secret locations for further enrichment, in part because Tehran has been less transparent about the number of centrifuges it has produced since 2021. 

The maximum pressure campaign that President Trump launched during his first term was continued by his successor (though enforcement was less strict under the Biden administration). Accordingly, Washington should be realistic in its expectations about what that policy can achieve—“max pressure” has now been in place longer than the JCPOA itself, and sanctions alone clearly cannot stop Iran from developing nuclear weapons. The regime has become accustomed to this type of pressure, so the only way to appreciably increase it is through measures such as pressuring China to stop buying Iranian oil or even forcibly interdicting Iranian oil shipments. Both options would carry significant risk of escalation now that Iran is so close to breakout, though they might also bring Tehran back to the table.  

Ultimately, a negotiated agreement remains the most durable path to halting Iran’s nuclear ambitions. Although the regime’s technical progress since 2018 has mooted many of the JCPOA’s most valuable elements (e.g., constraints on nuclear R&D and centrifuge site construction), a different, less comprehensive deal would still have value. Key elements of a new deal could include:

• greater IAEA access to relevant Iranian sites, especially those related to nuclear weaponization
• limits on uranium enrichment levels and stocks
• limits on the number of centrifuges deployed
• constraints on drone and missile proliferation

In return, Iran would no doubt insist on significant sanctions relief, leaving Washington and its allies with two options: limited relief of the type agreed to in the JCPOA, primarily affecting foreign business activity with Iran; or more comprehensive relief, possibly including major parts of the U.S. embargo. Whether such relief is reasonable to offer will depend squarely on what degree of nuclear and regional concessions the United States is able to extract. One idea floated by Michael Singh—renewable five-year deals—could be attractive to Tehran. 

Despite the ticking military clock, the parties have some time to work on these issues and explore a new deal. Nevertheless, it is important to remember that action and inaction both come with risks, and the available options for dealing with Iran’s nuclear program will only shrink over time.

Michael Eisenstadt

The goal of a preventive strike would be to maximize damage to the nuclear program and buy time to revive nuclear diplomacy, deter or disrupt attempts to rebuild, and create regional arrangements to contain a diminished Iran. Yet Tehran would almost certainly try to reconstitute the program using whatever fissile material, centrifuges, and personnel survived an attack, so prevention would likely not be a one-off event. Rather, it would likely be the opening round of a prolonged campaign to prevent Iran from rebuilding using covert action and follow-on strikes. And if Tehran became worried that subsequent attacks might include military, economic, and leadership targets, it could decide to slow-roll its rebuilding efforts.

To succeed, a preventive strike would also need to create an environment conducive to follow-on attacks. A successful first strike would make it easier to garner domestic and foreign support for subsequent action if deemed necessary. Avoiding escalation would likewise facilitate follow-on efforts—though Tehran’s ability to cause geopolitical disruptions has been greatly reduced by the evisceration of Hezbollah, the existence of robust regional air and missile defenses, and the damage done to Iran’s missile production capability during Israel’s October 2024 attack. Moreover, a strike on Iran’s enrichment facilities (which are mainly underground) would likely be contained, avoiding the kind of humanitarian disaster that an attack on a functioning nuclear reactor might have. To enable a prolonged campaign, the intelligence architecture and geopolitical environment that make follow-on attacks possible might have to be sustained for years to come.

Could Israel do the job on its own? Beyond conventional penetrator munitions for use against deeply buried targets, Israel has likely developed highly classified capabilities for this mission and has apparently used some of them during covert actions in recent years. Just as Israel’s pager attacks against Hezbollah last September confounded expectations of what a war between the two sides would look like, it is a fool’s errand to try surmising how Israel might attack Iran’s nuclear program. At the very least, Jerusalem would likely benefit from U.S. intelligence support and assistance in fending off Iranian retaliation. Yet a joint attack that brought U.S. and Israeli military capabilities to bear would no doubt be more effective.

Holly Dagres

Negative Iranian sentiment toward the regime has reached unprecedented levels. While the Iranian people previously blamed the West for sanctions and economic isolation pre-2015, they currently blame Tehran for their problems. This rising anti-regime sentiment also appears to correlate with dwindling public support for the nuclear program, which likely materialized after the 2017-18 protests and came to a head during the 2022 “Woman, Life, Freedom” uprising. Many Iranians also oppose reaching a new U.S.-Iran nuclear deal because they view it as throwing a lifeline to a regime they no longer want.

Among the pro-regime camp, some have defiantly advocated going all the way with the nuclear program, noting that the United States withdrew from the JCPOA and reimposed sanctions despite Tehran not violating the deal at the time. Others, however, are hoping for a new deal to provide a reprieve from the “resistance economy”—a term that Supreme Leader Khamenei coined to glorify Iran’s circumvention of sanctions by making its economy less dependent on international trade. Indeed, the economic situation on the ground has been deteriorating. Over the past few months, for example, twenty-one of Iran’s thirty-one provinces experienced power outages, the rial lost half its worth, and the price of potatoes skyrocketed 217 percent. 

Although the “Woman, Life, Freedom” uprising was unable to enact meaningful change, the recent fall of Syria’s Assad regime has renewed hope among those Iranians who dream of witnessing the fall of the Islamic Republic in their lifetime. The clerical establishment’s inability to address systemic mismanagement, corruption, and repression suggests that renewed anti-regime protests are on the horizon. Unfortunately, Tehran will likely respond to this sentiment by doubling down on its oppression, especially against women, girls, and minorities, who have long borne the brunt of such policies. 

This summary was prepared by Sary Mumayiz. The Policy Forum series is made possible through the generosity of the Florence and Robert Kaufman Family.