Murat SofuogluThe joint US-Israeli strikes during the 12-day war in June last year, and the subsequent tensions, were claimed to have severely damaged Iran’s nuclear infrastructure and depleted significant portions of its enriched uranium stockpile.
Yet despite repeated assertions by the Trump administration that Iran’s nuclear programme has effectively been dismantled, ongoing negotiations between Washington and Tehran continue to centre on a central question: the future of Iran’s enriched uranium.
For months, Washington insisted that any agreement must include zero enrichment, a position President Donald Trump repeatedly reiterated. Tehran, however, has consistently rejected that demand.
According to experts, the focus of the talks has now shifted toward reducing and managing Iran’s uranium enrichment program in accordance with the memorandum of understanding (MoU) signed by both sides.
An agreement on Tehran’s enrichment programme, which has reached 60 percent purity, just a technical step below weapons-grade levels, remains possible, though far from guaranteed, says Oral Toga, a researcher at the Ankara-based Centre for Iranian Studies.
A weapon-grade nuclear material typically requires enrichment levels of around 90 percent. According to estimates by the International Atomic Energy Agency, Iran possessed at least 440 kilograms of uranium enriched to 60 percent before the US-Israeli strikes in June.
Even after the attacks, IAEA chief Rafael Grossi has said that "a bit more than 200 kg" of the 60 percent stockpile likely survived within Isfahan’s tunnel complex.
The IAEA also estimates that Tehran held around 184 kilograms of uranium enriched to 20 percent purity and more than 6,000 kilograms enriched to five percent.
Taken together, Iran's stockpile contains enough nuclear material that, if further enriched to weapons-grade levels, could theoretically be used to produce at least 23 nuclear weapons, according to the agency's calculations.
“The June 17 Islamabad MoU already built the architecture for one, with a 60-day window to negotiate the final terms and a clause committing both sides to resolve the fate of the enriched stockpile through on-site downblending under International Atomic Energy Agency (IAEA) supervision as the baseline method,” Toga tells TRT World.
Under such an arrangement, Iran’s nuclear material would remain within the country, while IAEA inspectors would monitor and verify the downblending process, which would reduce enrichment levels to those deemed acceptable under a future agreement.
However, Toga notes that a significant gap remains between the memorandum itself, which envisions dilution rather than destruction of Iran’s enriched uranium, and what he describes as Washington’s continued “public maximalism” regarding the future of the program.
“The question is less whether a deal is technically reachable, since the dilution compromise already exists on paper, and more whether the US will honor what it signed or keep treating the memorandum, as Trump has, as merely an option it can discard,” he says.
“A framework on the stockpile is moderately likely; a deal that also ends enrichment outright is not.”
What will happen to Iran’s uranium?
Trump has previously asserted that Iran would deliver its uranium to the US, accepting its destruction.
"We will get it. We don't need it, we don't want it. We'll probably destroy it after we get it, but we're not going to let them have it," he said.
But according to Toga, there is little chance that Tehran will agree to hand over a stockpile that has become increasingly intertwined with questions of national security, sovereignty, and political prestige within the Iranian establishment.
Iran is unlikely to give up its enriched uranium “in the sense Washington's rhetoric demands, meaning physical surrender” to a third country or outright destruction, says Toga.
A May directive reportedly attributed to Supreme Leader Mojtaba Khamenei stated that the stockpile must not leave the country under any circumstances.
"The Supreme Leader’s directive, and the consensus within the establishment, is that the stockpile of enriched uranium should not leave the country,” an anonymous Iranian source told Reuters in May.
Instead, Tehran has indicated that it could accept downblending.
“What Iran has signaled it can accept is dilution. Even before the February strikes, Tehran had already offered during informal talks to downblend its 60 percent material to reactor grade,” says Toga.
The proposal resembles elements of the 2015 nuclear agreement, under which Iran limited enrichment to 3.67 percent, reduced its centrifuge capacity, and capped its stockpile at around 300 kilograms.
Tehran is effectively offering a similar arrangement today, although such a compromise may be politically difficult for the Trump administration to accept because it closely resembles the restrictions imposed under the Obama-era deal that Trump abandoned in 2018.
“The distinction is decisive. Downblending lets Iran keep the material on its own soil, frame the outcome as a managed civilian program rather than disarmament, and preserve the technical option of re-enrichment later, which is precisely why hawks in Washington reject it,” says Toga.
In practice, this would allow Iran to give up the weapons-relevant purity of its uranium without relinquishing ownership of the material itself.
Despite Khamenei’s reported directive, some Iranian sources believe Tehran could still consider a compromise involving a third country.
Under this scenario, roughly half of Iran’s stockpile enriched to 60 percent would be transferred to a country such as Russia, which has long played a significant role in Iran’s civilian nuclear programme.
In return, Tehran would receive uranium enriched to around five percent, while the remainder of its 60 percent stockpile would be diluted under IAEA supervision.
Mohammed Eslami, an Iranian academic and political scientist at the European University Institute, considers such an arrangement possible but unlikely under current circumstances.
“I believe an agreement on removal of highly enriched uranium has been achieved and by the end of the negotiations, there will be no 60% uranium in Iran. Either it will be downblended into lower levels, or it will be delivered to a third country,” Eslami tells TRT World.
Drawing on previous nuclear agreements involving the transfer of stockpiles abroad, Eslami nevertheless argues that downblending remains the most realistic path to resolving the impasse between Washington and Tehran.
The Trump administration has so far rejected proposals to transfer Iranian uranium to countries such as Russia or China, insisting that US custody of Tehran’s nuclear material remains the only acceptable arrangement.
Yet Eslami cautions against overstating the importance of the uranium issue in the broader negotiations.
According to him, discussions over sanctions relief, frozen Iranian assets, and the future status of the Strait of Hormuz may ultimately prove more consequential to the success or failure of any agreement than the fate of the enriched uranium stockpile itself.
How could enriched uranium be diluted?
Even if Washington and Tehran reach an understanding on the fate of Iran’s enriched uranium, significant questions remain about how roughly 440 kilograms of nuclear material could be recovered from the damaged underground facilities at Isfahan, Fordow, and Natanz.
“No one has a real idea on this,” says Toga, who remains sceptical about whether the US-Iran memorandum of understanding can be implemented in practice.
One of the key challenges, he notes, is determining how to access uranium that may now be buried beneath heavily damaged nuclear sites.
“The path written into the memorandum is to dilute Iran's enriched uranium on Iranian territory by mixing it with lower-grade uranium under IAEA monitoring, with a likely first step of converting it from gas to a more stable powder form to make handling safer. However, the difficulty here is not the chemistry but the verification process,” says Toga.
Since the US-Israeli strikes in June 2025, Iran has not granted the IAEA access to the affected facilities. As a result, uncertainty persists not only over the condition of the sites but also over how much enriched uranium survived the attacks and whether any material was moved beforehand.
“This is why inspector access is itself one of the live disputes, with Washington claiming Iran has agreed and Tehran saying inspections will only follow a final deal and the lifting of sanctions. Without that access, no dilution arrangement can be credibly confirmed,” says Toga.
The dispute over inspections underscores a broader problem facing the negotiations: even if the two sides agree on a technical solution for Iran’s uranium stockpile, implementing and verifying that agreement may prove far more difficult.
For that reason, Toga remains pessimistic about the prospects for a lasting breakthrough.
“I continue to see a resolution between them as a very difficult pitch,” he tells TRT World.
