US President Donald Trump is questioning why Iran has not yielded to mounting military pressure, according to special envoy Steve Witkoff.

"I don't want to use the word 'frustrated,' because he understands he has plenty of alternatives, but he's curious as to why they haven't ... I don't want to use the word 'capitulated,' but why they haven't capitulated," Witkoff said in an interview on Fox News on Sunday.

"Why, under this pressure, with the amount of sea power and naval power over there, why haven't they come to us and said: 'We profess we don't want a weapon, so here's what we're prepared to do'? And yet it's sort of hard to get them to that place."

The United States wants Iran to give up its supplies of enriched uranium, which Washington says could potentially be used to make a nuclear weapon, and to stop supporting militants in the Middle East and accept limits on its missile program.

"They've been enriching well beyond the number that you need for civil nuclear [purposes]," said Witkoff, claiming Tehran was enriching uranium "up to 60%" fissile purity.

"They're probably a week away from having industrial, industrial-grade bomb-making material, and that's really dangerous," he claimed.

Iran: 'If US attacks, we have every right to defend ourslves'
Iran insists its nuclear program is peaceful but says it is willing to accept some limitations in return for the lifting of financial sanctions.

Trump on Thursday gave Tehran 10 to 15 days to strike a deal on their long‑running nuclear dispute or face "really bad things," amid a US military buildup that has raised fears of a wider Middle East war.

Iranian President Masoud Pezeshkian ‌said ⁠​recent negotiations ​with the ​US "yielded ‌encouraging signals."

"We continue ‌to closely ‌monitor ​US actions and have ​made all necessary ⁠preparations ​for ​any potential ​scenario," he ‌said in a ​post ⁠on X.

Negotiations had reached an impasse after US and Iranian representatives met this week in Geneva.

The next round of US-Iranian talks will be on Thursday in Geneva, Oman's foreign minister said Sunday. Oman has mediated the negotiations.

Iranian Foreign Minister Abbas Araghchi warned on Sunday that his country would strike back at US interests in the Middle East in response to any military action.

"If the US attacks us, then we have every right to defend ourselves," he said in an interview with US network CBS. "If the US attacks us, that is an act of aggression. What we do in response is an act of self-defense."

Araghchi admitted that the Iranian military does not have the capability to hit targets on the US mainland, and so would therefore target American bases in the Middle East. "It is justified and legitimate," he said.

Nevertheless, in a previous interview with US network MS Now on Friday, Araghchi had said that Tehran expects to present a proposal to Washington "in the next two or three days," once it is approved by senior officials. The draft would then be forwarded to Witkoff.

Iranian students restart protests in Tehran
Meanwhile, students staged fresh protests at several Iranian universities on Sunday as the new academic semester got underway.

The demonstrations coincided with 40‑day mourning ceremonies for those killed in last month's government crackdown — the deadliest unrest in Iran since the 1979 Islamic Revolution.

Iranian state television broadcast videos of what it said were individuals "pretending to be students" attacking "pro-government students" in Tehran who were taking part in protests ​condemning the disturbances in January.

A video purportedly showed rows of marchers at Tehran's ​Sharif University of Technology condemning Supreme Leader Ayatollah Ali Khamenei as a "murderous leader," and calling for Reza ​Pahlavi, the ⁠exiled son of Iran's toppled shah, to return as monarch.

Earlier in February, Pahlavi said US military intervention in Iran could save lives, and urged Washington not to spend too long negotiating with Tehran's clerical rulers on a nuclear deal.

On Sunday, US special envoy Witkoff said he had met with Pahlavi at Trump's direction, but did not provide further details of the meeting.