Marathon talks between Iran and the United States, which began on Saturday in Islamabad, failed to reach an agreement.
Negotiations lasted 21 hours in Pakistan’s capital, marking the highest-level contact between the two sides since the 1979 Islamic Revolution.
The US delegation was led by Vice President JD Vance.
He said Washington was seeking a firm commitment from Iran that it would not develop a nuclear weapon.
But that commitment, he said after the talks ended, wasn't forthcoming.
However, he signalled that the US would give time to Iran to reconsider.
Meanwhile, according to Iranian state media, Tehran rejected a deal over what it described as unreasonable demands from the United States.
Both sides came to the negotiating table with differing sets of proposals. The US demanded full nuclear dismantlement, an end to uranium enrichment, and the reopening of the Strait of Hormuz.
Iran sought war reparations, the lifting of sanctions, control over the Strait of Hormuz, and a complete end to the conflict in the region, including halting Israeli attacks on Lebanon.
The negotiations were closely watched globally, for their likely far-reaching implications for West Asia's security, global energy markets, and international diplomacy.