«The fourth round of indirect Iran-US negotiations is concluded; difficult but useful talks to better understand each other’s positions and to find reasonable and realistic ways to address the differences,» ministry spokesman Esmaeil Baqaei said on X.

The next round will be co-ordinated and announced by Oman, he added.

A senior US official described Sunday’s talks positively, confirming another round would take place soon.

The discussions in Oman led by US special envoy Steve Witkoff «were again both direct and indirect, and lasted over three hours», a senior administration official said in a statement.

«Agreement was reached to move forward with the talks to continue working through technical elements. We are encouraged by today’s outcome and look forward to our next meeting, which will happen in the near future.»

Earlier in the day, Baqaei said Iran was «firmly determined to pursue its inalienable lawful rights for peaceful uses of nuclear energy … while fully prepared to continue its diplomatic engagement to ensure the already demonstrated ‘peaceful nature’ of its nuclear programme».

«We are equally resolved to work for termination of unlawful and inhuman sanctions that have long been imposed on our people.»

The talks in Muscat, the first round of which took place a month ago, follow a week-long pause after a meeting in Rome was postponed due to «logistical reasons», according to Oman’s Foreign Minister Badr Albusaidi, who has been mediating.

The discussions are the highest-level contact between the two foes since Washington withdrew in 2018 from a previous deal that sought to regulate Iran’s nuclear activities.

Steve Witkoff, the US envoy to the Middle East who is leading the US delegation, on Thursday said Iran’s uranium enrichment sites in Natanz, Fordow and Isfahan must be dismantled.

Iranian Foreign Minister Abbas Araghchi responded on Saturday night by saying Tehran will not back down on its “nuclear rights”. He told an Arab-Iranian conference in Doha that “if the goal of these talks is to ensure the non-acquisition of nuclear weapons, an agreement is possible. However, if the aim is to limit Iran’s nuclear rights, Iran will never retreat”, state media outlet Irna reported.

The latest round of talks come days ahead of a visit to the Gulf by US President Donald Trump, who will stop in the UAE, Saudi Arabia and Qatar.

Iran has repeatedly said its right to enrich uranium is «non-negotiable» and has ruled out a “zero enrichment” demand by some US officials. Before leaving for Muscat on Sunday, Araghchi reaffirmed that message, saying «enrichment capability is one of the honours and achievements of the Iranian nation».

Western powers suspect Tehran is seeking nuclear weapons. There have previously been mixed signals from Washington over whether it would settle for regulating enrichment or will insist on nuclear activities being dismantled.

Trump, who withdrew Washington from the 2015 deal between Tehran and world powers that was meant to curb Tehran’s nuclear activities, has threatened to bomb Iran if no new deal is reached to resolve the long-running dispute.

Tehran has accelerated its enrichment programme since the 2015 deal collapsed. It says it is purely for civilian purposes.

“In its indirect talks with the United States, Iran emphasises its right to peaceful use of nuclear energy and clearly declares that it is not seeking nuclear weapons,” Araghchi said.

“We continue our dialogues with the US government, and of course, simultaneously with Europe, Russia, and China, in good faith.”

He said “weapons of mass destruction have no place in Iran’s security doctrine. That is why we were among the initiators of creating a nuclear-weapon-free zone in the West Asian region”. “It is necessary for western countries and all those who claim to oppose nuclear weapons to refrain from double standards.”

Although the US and Iran have reported progress in the latest talks, few details have been released. Mr Trump is using a carrot-and-stick approach to persuade Iran to sign a new deal.

The US President has suggested Iran would be a “great, happy country” if it signs an agreement, but he has also pursued a “maximum pressure” campaign built around tough sanctions aimed at shutting off Iranian oil exports.