US President Donald Trump has endorsed what officials describe as a “final and best offer” to Iran after high-stakes nuclear negotiations in Islamabad ended without agreement, marking a significant setback in efforts to revive diplomatic engagement between the two sides.

Vice President JD Vance, who led the US delegation, confirmed that talks lasting more than 20 hours failed to produce a breakthrough despite what he described as “substantive discussions” with Iranian counterparts. He emphasized that the United States had entered negotiations in good faith but remained firm on its core demands.

“We leave here with a very simple proposal — our final and best offer,” Vance said, adding that it is now up to Iran to decide whether it is willing to accept the terms outlined by Washington.

According to US officials, President Trump was closely involved throughout the negotiations, maintaining frequent communication with the delegation. Vance noted that the team consulted the President multiple times during the talks, reflecting the high level of attention the White House placed on reaching an agreement.

At the center of the impasse is Washington’s insistence on long-term guarantees that Iran will not pursue nuclear weapons capability. US negotiators have sought a clear and verifiable commitment from Tehran not only in the immediate future but over the long term — a condition Iran has so far declined to accept.

“We need to see a fundamental commitment that they will not seek a nuclear weapon or the means to rapidly develop one,” Vance said, underscoring that temporary or limited assurances would not satisfy US security concerns.

Despite the breakdown, US officials maintained that their approach was flexible and aimed at finding common ground. However, key differences over verification measures, sanctions relief, and the scope of Iran’s nuclear activities proved too significant to overcome.

The collapse of the Islamabad talks comes at a time of heightened regional tensions and follows repeated attempts to restart dialogue over Iran’s nuclear programme. Previous rounds of negotiations have similarly stalled over trust deficits and conflicting strategic priorities.

While Washington has now put forward what it calls its final proposal, the path ahead remains uncertain. The failure to reach an agreement raises concerns about the future of diplomatic efforts and increases the risk of further escalation in an already volatile geopolitical environment.