U.S.’s and Israel’s war with Iran leaves uranium stockpiles uncertain

U.S.’s and Israel’s war with Iran leaves uranium stockpiles uncertain

By Dan Vergano edited by Claire Cameron

This past weekend the Trump administration and Israel started a war with Iran over the latter nation posing an imminent threat, chiefly because of its nuclear ambitions. The U.S. and Israel struck numerous military and leadership targets linked to the country’s uranium enrichment program. But the fate of Iran’s partly enriched uranium—the casus belli of the war—is unlikely to be settled by the conflict, nuclear nonproliferation experts say.

“Without effective monitoring, the whereabouts and security of Iran’s nuclear material will now become even more uncertain,” said Daryl Kimball, Thomas Countryman and Kelsey Davenport, nuclear nonproliferation experts at the Arms Control Association in Washington, D.C., in a statement released on Saturday.

The U.S. conflict is “not justifiable on nonproliferation grounds,” they said, adding that there were reports of progress toward a deal to curb Iran’s nuclear program before the war began.

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Last Friday, hours before U.S. bombs struck Tehran, the International Atomic Energy Agency (IAEA) released a report that indicated that Iran has not allowed inspections at any of its four declared uranium enrichment facilities since American and Israeli airstrikes on the three such sites that were then known to be operational were carried out last June.

Uranium needs to be concentrated, or enriched, into the isotope uranium 235 in order to serve as either nuclear reactor fuel or material for nuclear weapons. The IAEA estimated that Iran had 441 kilograms of 60 percent enriched uranium—enough for 10 nuclear weapons if the material were enriched further—before the June 2025 military action. It’s unclear how much remains after the most recent airstrikes, but U.S. and Iranian negotiations ahead of last Saturday’s strikes reportedly included the status of the stockpile, says nuclear safety expert Edwin Lyman of the Union of Concerned Scientists. That “would presume that it was still under Iran’s control,” he says.

Iran’s enrichment program was set back in the June 2025 airstrikes, says Ian Stewart of the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey. And the country’s leaders did not seem keen to rapidly rebuild it, perhaps because of fears of further conflict. “Iran now cannot quickly acquire nuclear weapons, but the risk is that an extremist could take charge and press ahead with the program,” he says.

“Now any attempt to recover that material or further process it, absent a diplomatic agreement and inspector access, would become an urgent issue requiring an even fuller intervention,” Stewart adds.

In January satellite imagery of the Isfahan nuclear enrichment facility suggested that Iran was possibly recovering uranium stocks from the bombed site. The U.S. and Israel reportedly struck Isfahan again this past weekend. In a statement on Monday, however, the IAEA’s director general Rafael Mariano Grossi said that “we have no indication” that any of Iran’s nuclear installations have been hit. “So far, no elevation of radiation levels above the usual background levels has been detected in countries bordering Iran,” Grossi said.

Even though it’s not fully enriched to weapons grade, Iran’s uranium stockpile affords a capability to build “several” nuclear explosive devices right now that would have “significant” yields, Lyman says. It may also be possible to deliver crude bombs by covert means, he adds. “But the potential cost to Iran of taking such a drastic step may well outweigh any benefits, given the unpredictability of how the U.S. and other nations might respond,” Lyman says.

Editor’s Note (3/2/26): This story is in development and may be updated.

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