The shift follows last weekend’s inconclusive talks in Islamabad, where big differences over Iran’s nuclear programme, including the fate of its enriched uranium stockpiles and how long Tehran should halt nuclear work, have continued to threaten progress, despite US officials and Pakistani mediators talking up prospects.
A senior Iranian official said the two sides had started to narrow some gaps, including over how to manage the Strait of Hormuz, a vital route for about 20% of the world’s oil and gas needs that has been closed to most ships for weeks.
Meanwhile, a source said that optimism grew that the Iran war may be near an end with a key Pakistani mediator having made a breakthrough on “sticky issues”, although Iran warned the fate of its nuclear programme had not been resolved.
Chief of Defence Forces (CDF) and Chief of the Army Staff Field Marshal Asim Munir, a key figure in the mediation, arrived in Tehran on Wednesday to try to prevent a renewal of the conflict after marathon talks held in Islamabad last weekend ended without a deal.
A senior Iranian official told Reuters that the trip had led to greater hopes for a second round of talks and an extension of the two-week ceasefire, but said fundamental differences remain over its nuclear programme.
Iran, which has faced crippling US sanctions for years, wants a memorandum to include Washington unfreezing some Iranian funds, in return for allowing more ships through the strait, said the senior official, who asked not to be named because of the sensitivity of the matter.
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A source briefed by Tehran said on Wednesday that Iran could let ships sail freely through the Omani side of the Strait of Hormuz without risk of attack under proposals it has offered in talks with the US, providing a durable deal is clinched.
But more than halfway through a two-week truce, deeper splits remain. The senior official said these included agreeing on the fate of Iran’s stockpile of highly enriched uranium (HEU), which the US wants removed, and the duration of any halt to Iranian nuclear work, notably uranium enrichment.
Iran has long demanded Washington acknowledge its right to enrich uranium, which Tehran says it only seeks for peaceful purposes, but which Western powers and Israel say is aimed at building nuclear weapons.
A Western diplomat said the nuclear issue “remains a core obstacle”.
If a memorandum to halt the conflict is reached, the two sides are expected to have 60 days to negotiate a final deal, which would require the involvement of experts and the International Atomic Energy Agency (IAEA), the Iranian sources said.
A previous international deal curtailing Iran’s nuclear work in return for sanctions relief was signed in 2015, but it took almost two years to negotiate. President Donald Trump scrapped that pact in 2018.
The Iranian sources said the United States is demanding a halt to Iran’s nuclear enrichment work for 20 years, while Iran wants to limit it to three to five years. Tehran also wants a timetable for lifting sanctions of the UN, US and EU, they said.
Iran has also in the past refused a US demand to ship out its entire stockpile of uranium, which has been enriched to 60%, a level that is far higher than levels needed for civilian uses.
However, Iranian sources said there were signs a compromise could emerge. One source said that, while Iran was not ready to send all its highly enriched uranium (HEU) abroad, part of it could be sent to a third country.
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He said some HEU was needed for medical purposes and for a research reactor in Tehran, which runs on relatively small amounts of uranium enriched to around 20%.
The IAEA estimates Iran had 440.9kg of uranium enriched to 60% when Israel and the US launched their first attacks on Iranian nuclear facilities in June 2025. Exactly how much of that has survived is unclear.
IAEA chief Rafael Grossi said in March that what remained of that stock was “mainly” stored in a tunnel complex in Isfahan, and that his agency believed slightly more than 200kg of it was there. It also believes some is at the sprawling nuclear complex at Natanz, where Iran had two enrichment plants.
A second Western diplomat said: “The 440kg HEU remains cause for concern because it allows Iran to have what we call sufficient quantities to build a number of nuclear bombs quite quickly, because the final enrichment phase is relatively quick.”