Strikes may set Iran back — but likely won't end nuclear program, UN watchdog chief warns

The United Nations' nuclear watchdog chief says Iran’s enriched uranium stockpiles remain largely in place and its nuclear infrastructure — much of it buried deep underground — cannot be fully eliminated by airstrikes, underscoring the limits of military action.

The head of the United Nations’ nuclear watchdog suggested to reporters Wednesday Iran’s nuclear program is unlikely to be eliminated through military force, warning that ongoing U.S. and Israeli strikes cannot fully dismantle Tehran’s capabilities.

Asked directly whether the program could be resolved militarily, International Atomic Energy Agency Director General Rafael Grossi said he did not believe it could.

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"This program is a very vast program," Grossi said, describing a network of facilities, expertise and infrastructure built throughout decades. "At the end of this … the material will still be there, the enrichment capacities will be there."

"We will have to go back to some form of negotiation," he said. 

Grossi emphasized he does not offer military advice, framing his comments as a technical assessment of the program’s scope.

The nuclear inspector said the agency’s assessment is that Iran’s enriched uranium stockpile remains largely where it was prior to the strikes, with most of the material believed to be at the Isfahan nuclear complex and smaller amounts at Natanz.

"Our assumption is that the material is … where it was," he said. 

That reality underscores a broader challenge: much of Iran’s most sensitive nuclear infrastructure — including storage sites for enriched uranium — is buried deep underground, making it difficult to destroy through airstrikes alone.

While U.S. and Israeli strikes have degraded parts of Iran’s nuclear program, including above-ground facilities and support infrastructure, they have not eliminated the core components of the program.

That assessment aligns with previous reporting on the limits of military action against Iran’s nuclear program. Analysts say highly enriched uranium stored at sites like Isfahan is believed to be kept deep underground in relatively mobile containers, making it difficult to destroy or secure without direct access to the facilities.

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"It’s not even clear the United States knows where all of the uranium is," Kelsey Davenport, director of nonproliferation policy at the Arms Control Association, previously told Fox News Digital, noting that the mobility of storage containers raises the possibility that some material could be moved or dispersed.

Iran possessed roughly 441 kilograms of uranium enriched to 60% as of mid-2025 — enough, if further enriched, to fuel multiple nuclear weapons, according to the International Atomic Energy Agency. 

Experts estimate the final step to weapons-grade enrichment could take weeks under ideal conditions, though building a deliverable weapon would require additional time for weaponization and delivery systems.

Grossi also pointed to continued uncertainty surrounding a newly disclosed enrichment facility near Isfahan.

The site is believed to be a newly declared underground enrichment facility where Iran could potentially install centrifuges to produce enriched uranium. Grossi said the International Atomic Energy Agency has not yet inspected the location and does not know whether it is operational, under construction or equipped with nuclear material.

"We know where it is… but we have not been able to go," he said.

Grossi said the agency has not been able to access some sites during the conflict and is relying in part on imagery to assess conditions.

The gaps in access highlight the limits of current monitoring. Grossi acknowledged the agency lacks full visibility into some parts of Iran’s program, particularly sites it has not been able to inspect.