Iran said on Friday it expected to hold more negotiations with the United States, hailing a "positive atmosphere" during a day of talks in Oman but warning against threats after Washington raised the spectre of new military action.

The talks were the first between the two countries since the United States joined Israel's war with Iran in June with strikes on nuclear sites.

Foreign Minister Abbas Araghchi, who led Iran's delegation in Muscat, said talks "focused exclusively" on the Iranian nuclear programme, which the West believes is aimed at making an atomic bomb but Tehran insists is peaceful.

The US delegation, led by Middle East envoy Steve Witkoff and US President Donald Trump's influential son-in-law Jared Kushner, had also wanted Tehran's backing for militant groups, its ballistic missile programme and treatment of protesters on the agenda.

"In a very positive atmosphere, our arguments were exchanged and the views of the other side were shared with us," Araghchi told Iranian state TV, adding that the two sides had "agreed to continue negotiations, but we will decide on the modalities and timing at a later date".

Speaking to the official IRNA news agency, he expressed hope that Washington would refrain from "threats and pressure" so that "the talks can continue".

There was no immediate comment from the American delegation in Muscat. (AFP)