WASHINGTON -- Marathon talks aimed at halting the war in Iran failed without a breakthrough, as US Vice President JD Vance flew back to the United States amid major questions what comes next for the 43-day-old conflict.
Before departing Pakistan on April 12, Vance called the talks -- the highest-level talks between Washington and Tehran in decades -- "substantive" but said Iran had balked at Washington's core security demands.
"We leave here with a very simple proposal, a method of understanding that is our final and best offer. We'll see if the Iranians accept it," he said.
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WATCH: US Vice President's Statement After Marathon Iran Talks
Esmail Baqaei, a spokesman for Iran's Foreign Ministry, said about the two sides reached an understanding "on a number of issues."
However, "there were differences of opinion on two or three important issues, and ultimately the talks did not lead to an agreement," he said in a post to social media.
The Nuclear 'Red Line'
Speaking to reporters after the talks concluded, Vance suggested Tehran was to blame for the impasse.
US Vice President JD Vance's news conference is broadcast on Pakistani TV early on April 12.
"We have been at it now for 21 hours... We've had a number of substantive discussions with the Iranians. That's the good news," Vance said. "The bad news is that we have not reached an agreement. And I think that's bad news for Iran much more than it's bad news for the United States."
The US "red lines," Vance said, centered on securing an "affirmative commitment" that Tehran will not seek a nuclear weapon, or the means to do so, which he said is a "core goal" of the administration.
“The simple question is: Do we see a fundamental commitment of will for the Iranians not to develop a nuclear weapon...for the long term?" Vance asked. "We haven't seen that yet."
Iran's nuclear ambitions dominated the talks, but Vance said the agenda included other major issues, including frozen assets and broader tensions in the Middle East.
He declined to go into detail, saying he would not "negotiate in public" after nearly a day of private deliberation.
Vance said he was in contact with US President Donald Trump and top administration officials throughout the talks.
Tehran's Defiance, And The Specter of Escalation
In his post to X, Baqaei called on Washington to "refrain from excessive demands and unlawful requests" and accept Iran's "legitimate rights and interests."
He characterized the "intensive" sessions as covering a wide range of issues, including the Strait of Hormuz, war reparations, and the "complete end of the war against Iran."
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Multiple Hurdles To Peace As US, Iranian Delegations GatherState-aligned media in Tehran, meanwhile, accused Washington of "breaches of promise" and "malicious acts."
The collapse of the talks sparked concern that the fighting will intensify.
"Iran's regime feels it's winning," said Jason Brodsky, policy director at United Against Nuclear Iran, a nonprofit research organization. "This is emboldening Tehran to refuse once again US offer."
"But it risks overplaying its hand," he told RFE/RL. "The US has to change the Iranian decision-making calculus to shatter that perception of victory. This sets the stage for a military escalation."