Iranian Foreign Minister Abbas Araghchi and Donald Trump's Middle East envoy Steve Witkoff are leading their delegations at the negotiations in Oman, which acts as a mediator between the countries.
Iranian state media reported the talks had begun, with Araghchi saying Tehran maintains "full readiness to defend the country's sovereignty and national security against any excessive demands or adventurism" by the United States.
"Iran enters diplomacy with open eyes and a steady memory of the past year. We engage in good faith and stand firm on our rights," Araghchi added on X.
"Commitments need to be honoured. Equal standing, mutual respect and mutual interest are not rhetoric -- they are a must and the pillars of a durable agreement," he said.
The Omani Minister of Foreign Affairs, Badr bin Hamad Al Busaidi held separate consultations with the Iranian delegation, the Omani Ministry said in a statement.
"The consultations were aimed at creating suitable conditions for resuming diplomatic and technical negotiations, while underscoring their importance given all parties’ commitment to ensuring successful talks that would sustain regional security and stability," read the text.
Iranian News Agency said Araghchi met for the second time with his Omani counterpart as part of the negotiations with Washington.
On Thursday, diplomatic sources said the talks were expected to be held face-to-face, but by Friday the pre-discussions appeared to remain indirect, conducted through Omani mediators.
The Wall Street Journal cited a source as saying that the head of US military forces in the Middle East would join the latest talks.
But on Friday, Iran warned that any involvement by US military or regional defence officials in talks with could jeopardise the negotiations.
The talks were initially scheduled for Friday in Ankara, and Turkey had already sent invitations to Egypt, Qatar and Saudi Arabia. “But the subsequent expansion of the invitations irritated the Iranians,” an Egyptian source told Ahram Online, explaining the shift in venue to Oman.
'Solely Nuclear'
Iran has insisted the Oman-mediated talks will be centred solely on its nuclear programme, though the United States also wants to discuss Tehran's backing for militant groups in the region and its ballistic missile programme.
The talks are the first since the US bombed Iranian nuclear facilities last June during a 12-day Israeli war on the country, ending a previous round of discussions.
Iran had said on Thursday it had a "responsibility not to miss any opportunity to use diplomacy" to preserve peace, adding it hoped Washington would participate in the discussions "with responsibility, realism and seriousness".
The US delegation intends to explore "zero nuclear capacity" for Iran, White House Press Secretary Karoline Leavitt said, warning that Trump had "many options at his disposal aside from diplomacy".
The meeting comes just under a month after the peak of nationwide protests in Iran, initially driven by rising living costs, which Tehran has accused the United States and Israel of hijacking through support for violent unrest.
Trump initially threatened military action against Tehran, framing Iran’s response to internal unrest as justification and signaling support for demonstrators by claiming that “help is on its way.”
In recent days, however, his rhetoric has shifted toward reining in Iran’s nuclear programme, which the United States and Israel on top have, for decades, repeatedly accused, without substantial evidence, of being perpetually on the verge of producing a bomb.
"They're negotiating," Trump said of Iran on Thursday.
"They don't want us to hit them, we have a big fleet going there," he added, referring to the aircraft carrier group he has repeatedly called an "armada".
US Vice President JD Vance told SiriusXM in an interview broadcast Wednesday that Trump would "keep his options open".
"He is going to talk to everybody, he is going to try to accomplish what he can through non-military means and if he feels like the military is the only option then he is ultimately going to choose that," Vance said.
'Unilateral bullying'
Turkish President Recep Tayyip Erdogan was quoted by Turkish newspapers as saying: "So far, I see that the parties want to make room for diplomacy," adding that conflict was "not the solution".
China said it supports Iran defending its interests and opposes "unilateral bullying".
There had been disagreement in the run-up to the talks over whether the meeting should also include regional countries and address Tehran's support of militant groups and its ballistic missile programmes, two US concerns that Iran resisted.
Citing unnamed Iranian officials, the New York Times said the United States agreed the talks would exclude regional actors, and while the meeting would focus on the nuclear issue, it would also discuss missiles and militant groups "with the goal of coming up with a framework for a deal".
With the American threats of military action still looming, the United States has sharply escalated by moving a naval group led by aircraft carrier USS Abraham Lincoln into the region.
Iran has repeatedly vowed it will hit back at US bases if attacked.
"We are ready to defend and it is the US president who must choose between compromise or war," state television on Thursday quoted army spokesman General Mohammad Akraminia as saying, warning that Iran has "easy" access to US regional bases.
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