Iran and US delegates vow more talks after Oman meeting

Iran and the United States have agreed to continue nuclear talks next week, both sides say, although Iranian Foreign Minister Abbas Araqchi says he is "cautious" about the success of the negotiations to resolve a decades-long stand-off.

US President Donald Trump has signalled confidence in clinching a new pact with the Islamic Republic that would block Iran's path to a nuclear bomb.

Araqchi and Trump's Middle East envoy Steve Witkoff held a third round of the talks in Muscat through Omani mediators for about six hours, a week after a second round in Rome that both sides described as constructive.

"The negotiations are extremely serious and technical ... there are still differences, both on major issues and on details," Araqchi told Iranian state TV.

"There is seriousness and determination on both sides ... However, our optimism about success of the talks remains extremely cautious."

A senior US administration official described the talks as positive and productive, adding that both sides agreed to meet again in Europe "soon".

"There is still much to do but further progress was made on getting to a deal," the official added.

Earlier Omani Foreign Minister Badr Albusaidi had said talks would continue next week, with another "high-level meeting" provisionally scheduled for May 3.

Araqchi said Oman would announce the venue.

Ahead of the lead negotiators' meeting, expert-level indirect talks took place in Muscat to design a framework for a potential nuclear deal.

"The presence of experts was beneficial ... we will return to our capitals for further reviews to see how disagreements can be reduced," Araqchi said.

An Iranian official, briefed about the talks, told Reuters earlier that the expert-level negotiations were "difficult, complicated and serious".

The only aim of these talks, Araqchi said, was "to build confidence about the peaceful nature of Iran's nuclear program in exchange for sanctions relief".

While both Iran and the United States have said they are set on pursuing diplomacy, they remain far apart on a dispute that has rumbled on for more than two decades.

Trump, who has restored a "maximum pressure" campaign on Iran since February, ditched a 2015 nuclear pact between Iran and six world powers in 2018 during his first term and reimposed crippling sanctions on Iran.

Since 2019, Iran has breached the pact's nuclear curbs including "dramatically" accelerating its enrichment of uranium to up to 60 per cent purity, close to the roughly 90 per cent level that is weapons grade, according to the United Nations nuclear watchdog.

US Secretary of State Marco Rubio said this week Iran would have to entirely stop enriching uranium under a deal, and import any enriched uranium it needed to fuel its sole functioning atomic energy plant at Bushehr.

Iran is willing to negotiate some curbs on its nuclear work in return for the lifting of sanctions, according to Iranian officials, but ending its enrichment program or surrendering its enriched uranium stockpile are among "Iran's red lines that could not be compromised" in the talks.

Moreover, European countries have suggested to US negotiators that a comprehensive deal should include limits preventing Iran from acquiring or finalising the capacity to put a nuclear warhead on a ballistic missile, several European diplomats said.

Iran insists its defence capabilities like its missile program are not negotiable.