Washington DC - Iran and the US said Wednesday they were going ahead with nuclear talks in Oman later this week, even as President Donald Trump piled pressure on Tehran's supreme leader by saying he should be "very worried."

Doubts had swirled about the fate of the negotiations after a report earlier Wednesday that the talks between the bitter foes were falling apart due to disagreements about the format and the venue.

The uncertainty had increased fears of renewed US military action against Tehran, amid soaring tensions since Iran violently put down some of the most serious protests against its rule since the 1979 Islamic revolution.

But Iranian Foreign Minister Abbas Araghchi said nuclear talks were now "scheduled" for Friday in Muscat.

"I'm grateful to our Omani brothers for making all necessary arrangements," he said on X.

A White House official also confirmed to AFP that the meeting would happen in Oman on Friday.

Diplomats had earlier said the meeting would happen in Turkey. But the Axios news outlet said the US was on the verge of pulling out, as Iran disputed both the location and whether its ballistic missile program should be included.

But Trump, who has sharply built up the US military presence in the region and refused to rule out new military action, continued to ramp up the pressure on Ayatollah Ali Khamenei.

"I would say he should be very worried," Trump said Wednesday in an interview with NBC News.