• Foreign & Public Diplomacy
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July 25, 2025, 10:30 AM View Comments ()

Immediately after the United States attacked Iranian nuclear facilities on June 21, President Donald Trump declared the operation a “spectacular military success.” Since then, his administration has been searching for ways to back up this statement. It has settled on the argument, apparently advanced by a new classified intelligence assessment, that Iran would need “years” to rebuild the facilities hit last month.

This claim has the advantage of being true—but it is also disingenuous.

Iran does not need to rebuild its previous nuclear program to build the bomb. Both the United States and Israel believe, with good reason, that most of Iran’s stockpile of highly enriched uranium (HEU) survived the attack. Tehran likely also retains the capability to further enrich and then weaponize this material to produce a handful of nuclear weapons. If Tehran decides to proceed down this route, it could likely manufacture its first bomb within a year, despite the Trump administration’s implication to the contrary.

Prior to the onset of the Iran-Israel war, most of Iran’s HEU stockpile, which included about 400 kilograms of HEU enriched to 60 percent, was stored in tunnels under its nuclear complex at Esfahan. There’s apparently disagreement among intelligence agencies about whether Iran moved some or all of that material before the Israeli strikes, though Israel and the United States seem increasingly confident that it did not.

The tunnels at Esfahan are deep—so deep that the United States did not even try to collapse them with the bunker busters it dropped on Iran’s enrichment plants at Fordow and Natanz. It may have launched cruise missiles against the tunnel entrances to try to seal them. However, Iran likely reduced the already modest benefits of this approach by preemptively filling the tunnel entrances itself.

As a result, repeated claims by U.S. and Israeli officials that Iran’s HEU is “buried beneath rubble” are misleading. Assuming the material wasn’t moved, it is now sitting unsquashed in intact tunnels. The implication in the New York Times’ recent reporting that Iran may struggle to recover it (“even if the Iranians can dig [the HEU] out…”) is nearly comical. The shovel is an adequate level of technology for tunnel unblocking, though bulldozers and excavators (which Iran possesses) would certainly speed things up. Indeed, Iran unblocked the entrance to one tunnel at Esfahan within a week of the strike (though it is not possible to determine from open-source information whether that tunnel is part of the network used for HEU storage).

In short, it is highly likely that most of Iran’s HEU survived the strikes and is accessible. Israel and the United States reportedly hope to deter Iran from removing it by the threat of further military action—but there’s no meaningful technical barrier to Iran’s doing so.

If Iran decided to build the bomb, its next step would be to enrich this material further. Unfortunately, the more enriched uranium is, the easier further enrichment becomes. As a result, Iran could make do with a centrifuge facility much smaller than the now-destroyed industrial-scale plants at Fordow or Natanz (which were designed to accommodate thousands and tens of thousands of centrifuges, respectively). I estimate that with fewer than 200 centrifuges and using 60 percent HEU as feedstock, Iran could produce one bomb’s worth of 90 percent HEU in just 10 to 20 days.

Iran may already have such an enrichment plant, hidden in plain sight in an anonymous industrial building or, more likely, located deep underground beyond the reach of U.S. bunker busters. But even if it does not, it could likely set one up in months using its large stockpile of centrifuge components. These parts stopped being monitored by the International Atomic Energy Agency in 2021 as the Iran deal progressively fell apart following the United States’ withdrawal.

According to U.S. officials, however, none of this matters now that the United States has deprived Iran of the capabilities needed to turn HEU into a usable weapon. For example, Secretary of State Marco Rubio has argued that the United States “wiped out” Iran’s conversion facility and “you can’t do a nuclear weapon without” one.

Rubio is quite right that conversion—the production of uranium metal from the uranium hexafluoride used in enrichment—is a necessary step in building a nuclear weapon. However, he is quite wrong in his implication that the destruction of the Esfahan conversion facilities (there were two of them, actually) dealt a crippling blow to Iran’s ability to build the bomb.

Conversion just isn’t difficult, as the United States’ own experience demonstrates. During the Manhattan Project, the many daunting technical challenges that U.S. scientists had to overcome did not include the production of uranium metal. The United States developed the necessary process in the chemistry department of Iowa State College at Ames (now Iowa State University) using equipment installed in the 1920s. Just eight months after research began, scientists there were churning out 50 kg of metal per week—enough, in principle, for at least two nuclear weapons.

I say “in principle” because the material produced in Iowa was destined to be reactor fuel; it was not enriched and was insufficiently pure to be used in a weapon. However, the Los Alamos team needed to make only slight tweaks to the Ames process to produce the highly pure, highly enriched uranium metal that fueled the bomb that destroyed Hiroshima.

Iran, for its part, has already conducted extensive experiments in this area and has probably perfected a recipe for producing pure uranium metal. In the unlikely event there is not a single laboratory in the entire country that is suitably equipped for this process, Iran could set one up rapidly and quietly. The necessary equipment (such as furnaces) and materials (such as high-purity calcium or magnesium) are widely available.

In addition to producing HEU metal, Iran would also have to finish its nuclear-weapon design and manufacture the components, nuclear and nonnuclear. This process could likely be completed in a year—possibly much less—and could largely run in parallel with enrichment and metal production.

Arguing that Iran would need years to rebuild its previous nuclear program is, therefore, like asserting that an unlocked bank vault would be impervious to a cyberattack; it’s true but misses the point.

To be sure, we don’t know whether Iran has made the political decision to proliferate. But the United States needs to grapple with the reality that its military operation increased Iran’s incentives to build the bomb while only marginally and temporarily setting back its capabilities to do so.

Repeated military strikes on Iran’s nuclear facilities—“mowing the grass” as it’s euphemistically called—is unlikely to prove either politically sustainable or effective. If the United States could destroy Iran’s HEU and centrifuge components, it would surely have done so. Instead, what Washington has succeeded in doing is showing Iran the limits of its ability to destroy deeply buried facilities.

What’s left is diplomacy, which is more promising than military action, even though it will still prove exceptionally challenging. By kicking out inspectors and threatening to withdraw from the Nuclear Nonproliferation Treaty, Iran has succeeded in producing an uncomfortable amount of leverage for itself. This means a perfect deal will not be attainable, and Washington would be wise to set clear priorities. Zero enrichment—the Trump administration’s stated goal—would always be nice to have. However, the restoration of inspector access, including to potential secret nuclear facilities, is truly vital. It’s not clear whether Washington could even attain this bare minimum right now—but there’s only one way to find out.