The fate of Iran’s nuclear programme, and attempts by the US and Israel to destroy it, could hang on the Islamic republic’s more than 400kg of uranium enriched to levels just short of weapons-grade.
After US stealth bombers dropped huge 30,000lb bunker-buster bombs on Iran’s main nuclear sites, Donald Trump claimed the “key nuclear enrichment facilities have been completely and totally obliterated”.
There is little doubt that the sites Tehran has been using to produce highly enriched uranium – Natanz and Fordow – have suffered severe damage. A third site in Isfahan, used in the fuel cycle but also for storage, was hit by Tomahawk cruise missiles launched from an American submarine.
But as the Trump administration conducts its damage assessment, the critical question will be whether Iran’s programme has been destroyed, or simply pushed into smaller, secret facilities that are harder to find.
The answer depends significantly on what has happened to Iran’s 408kg stockpile of uranium enriched to 60 per cent purity – approaching the 90 per cent purity required for weapons.
“It comes down to the material and where it is,” said Richard Nephew, a former senior US official who worked on Iran in the Obama and Biden administrations. “On the basis of what we’ve seen at this point, we don’t know where the material is. We don’t have any real confidence that we’ve got the ability to get it any time soon.”
“I think you would be foolish,” he added, “if you said that the programme was delayed by anything more than a few months.”
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Marco Rubio, US secretary of state, said “no one will know for sure for days” whether Iran attempted or was able to move highly enriched uranium.
“I doubt they moved it, because you really can’t move anything right now,” he told CBS. “The minute a truck starts driving somewhere, the Israelis have seen it, and they’ve targeted it and taken it out.”
But an Iranian regime insider said it would have been “very naive to keep our enriched uranium in those sites”, adding: “The enriched uranium is untouched now.”
He added that Iran – which has always insisted its programme is for peaceful, civilian purposes – would not seek to weaponise its programme. As hostilities with Israel have intensified, other Iranian officials have hinted that Tehran could look to alter its nuclear doctrine.
Analysts have warned Tehran could rush to develop a bomb using clandestine facilities if it becomes desperate and feels the need to restore its deterrent.
Ali Shamkhani, senior adviser to Iran’s supreme leader, said the country’s nuclear abilities remained steadfast. “Even if nuclear sites are destroyed, [the] game isn’t over,” he wrote on X.
“Enriched materials, indigenous knowledge, political will remain,” said Shamkhani, who was reported to have been wounded in Israel’s first round of strikes more than a week ago.
The highly enriched uranium had been held at Natanz, in central Iran; Fordow, the main enrichment facility dug deep into a mountain near the holy city of Qom; and in tunnels at the Isfahan site, Nephew said.
Once cooled, it is stored in powder form in large cylinders similar to a water heater.
The stockpile of uranium enriched to 60 per cent – part of an overall stockpile of more than 8,400kg, the majority of it low-level purity – meant Tehran had the capacity to produce sufficient fissile material required for several nuclear bombs within days if it chose.
But the actual weaponisation process would be expected to take months or a year, experts said.
The risk was always that after Israel launched its bombing campaign on the pretext of destroying Tehran’s nuclear programme, Iran would secretly take the stockpile to hidden locations, where advanced centrifuges had been covertly set up.
Nephew said the “unknowns here are killing us a little bit”.
“If they’ve got a uranium conversion line set up ... and if they were able to enrich up to 90 per cent at Fordow before it was attacked, and they had eight or nine days, that’s potentially enough for two bombs’ worth of 90 per cent,” he said.
India, Pakistan and North Korea all successfully developed covert nuclear weapons programmes despite onerous surveillance and restrictions from the US.
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Sima Shine, a former Iran specialist at Mossad, the Israeli intelligence agency, said she was convinced Iran had moved enriched material.
“They have enough enriched uranium somewhere, and they took some advanced centrifuges somewhere, in order to enable them to some day go to a nuclear device,” Shine said. “The programme is not destroyed completely, no matter what the Americans say.”
One Israeli official said that if Tehran and Washington resumed talks on allowing Iran to have a peaceful nuclear energy programme, Israeli prime minister Binyamin Netanyahu might insist Tehran hand over any highly enriched uranium to be transported and stored outside the country.
A second official acknowledged that Iran could have spirited away at least some of its highly enriched stockpile. But the officials added that after Israel last week assassinated at least 11 Iranian nuclear scientists, the regime would struggle to create an “efficient, miniaturised nuclear weapon”.
The International Atomic Energy Agency has inspectors in the republic who frequently visit Fordow, Natanz and other declared facilities. But Israel’s bombing campaign put a halt to those inspections.
Even before the strikes, the UN nuclear watchdog lacked oversight over all of the thousands of advanced centrifuges Iran developed after Trump in his first term pulled out of the 2015 nuclear deal that severely restricted Tehran’s activity.
Iran’s co-operation with the IAEA had also severely deteriorated in recent years, impeding the agency’s ability to conduct inspections to the level agreed in the 2015 agreement.
After Iran was censured in an IAEA resolution, days before Israel launched its attack, Iran also revealed that it had built a previously undeclared enrichment facility – the country’s third.
Israel targeted the Natanz facility on the first day of its strikes and has hit it again, causing damage to its overground and underground plants, the IAEA said last week. Israel also hit the Isfahan site twice.
But it lacked the military capacity to cause significant damage to Fordow and waited for the US’s intervention.
“It’s certainly the end of the Iranian nuclear programme as we knew it,” said Ali Vaez, an Iran expert at Crisis Group. “If the programme survives, it’ll either become a clandestine weapons programme or, in case of a deal, a neutered civilian programme without access to nuclear fuel cycle technology.” – Copyright The Financial Times Limited 2025
