Iran and the United States failed to reach an agreement to end the war in the Middle East, US Vice President JD Vance said Sunday after marathon talks in Islamabad, adding that he was leaving negotiations after giving Tehran the "final and best offer".

Vance said Washington was seeking a "fundamental commitment" from Iran that it would not develop a nuclear weapon, but that "we haven''t seen that" after holding the highest-level meeting between the two sides since the 1979 Islamic revolution.

However, he signalled that he was still giving time to Iran to consider the offer from the United States, which on Tuesday said it would pause attacks with Israel for two weeks pending negotiations.

The United States and Israel had attacked Iran on 28 February, sparking retaliation from Tehran that has plunged the Middle East into conflict and the global economy into tumult.

Iran and the US had entered the talks mediated by Pakistan with maximalist positions, with Washington also piling pressure by saying it had sent minesweeping ships through the vital Strait of Hormuz.

Signs of strain in the negotiations appeared when Iranian media accused the United States of making "excessive demands" on the Strait of Hormuz, through which one-fifth of the world's oil transits.

Separately, US President Donald Trump also contended several hours into the talks on Saturday, he did not care about the outcome.