Before U.S. negotiators could take off for a second round of face-to-face talks with Iran, the Trump administration’s hopes for a quick diplomatic breakthrough came crashing down when the Iranian regime failed to return messages seen as critical to setting the stage for a deal, multiple officials and other sources tell ABC News. 

In the days before the two-week ceasefire between the countries was set to end, sources say that the U.S. floated a list of broad points it hoped Iranian officials would approve of before a second meeting in Islamabad. 

Both sides had been swapping messages and proposals, but as the deadline drew closer, communication started to lag. By Tuesday afternoon, with just hours until the ceasefire’s expiration, Iran had still not submitted a response to the administration’s list or provided any assurance it would send a high-level delegation to the talks, the sources said. 

At this point, Air Force Two — which had been readied to transport Vice President JD Vance to Pakistan — had been sitting empty on a Joint Base Andrews tarmac for hours. The government plane that had been slated to carry the other lead negotiators, special envoy Steve Witkoff and Jared Kushner, had been redirected to Washington so all three could huddle at the White House with the president and his other top advisers.

Officials briefed on the meeting said it was quickly apparent that the talks could not go forward as planned, but that Trump ultimately elected to give diplomacy more time to play out. 

Just after 4 p.m., Trump announced in a post on his social media platform that he had decided to extend the ceasefire until the “seriously fractured” government of Iran could submit “a unified proposal” and “discussions are concluded, one way or the other.” 

The Trump administration assesses that these fractures among Iran’s leadership are behind the lack of response to its proposed terms, officials said, and that serious concerns about the regime’s ability to unify behind any diplomatic agreement with the U.S. has been an undercurrent through negotiations following the outbreak of war with Iran. 

Sources with knowledge of the negotiations say there are still major gaps between the sides on key issues — particularly what to do about Iran’s stockpile of highly enriched uranium, whether Iran will be allowed to enrich uranium in the future and under what conditions. 

Pakistan has emerged as the lead mediator in the talks, but one Pakistani official told ABC News that these outstanding differences between the U.S. and Iranian positions appear insurmountable. 

However, Trump administration officials maintain there is a possibility that a deal can be reached and say that the U.S. is still awaiting Iran’s counterproposal. 

Trump has not said for how long he would extend the ceasefire and the White House declined on Wednesday to publicly set any deadline. 

“Look, I think President Trump ultimately will dictate the timeline, and he will do so when he feels is in the best interest of the United States and the American people,” White House press secretary Karoline Leavitt said Wednesday. 

Trump himself also appeared to be downplaying the idea that time pressure was at play in the negotiations — but implied the ongoing U.S. naval blockade of Iranian ports would bring the regime to the table. 

“The blockade scares them even more than the bombing,” he told Fox News. “They’ve been bombed for years but the blockade, they hate.”

ABC’s Mary Bruce, Isabella Murray, Michelle Stoddart and Emily Chang contributed to this report.