A sixth round of nuclear talks between Iran and the United States planned for this weekend has been cancelled, mediator Oman said Saturday, as Iran and Israel traded massive strikes in their fiercest confrontation yet.

The talks on Iran's nuclear program began in April, with US President Donald Trump threatening military action if diplomacy failed.

"The Iran US talks scheduled to be held in Muscat this Sunday will not now take place," Omani Foreign Minister Badr Albusaidi said in a post on X.

"Diplomacy and dialogue remain the only pathway to lasting peace," he added.

A major sticking point in the lead-up to Sunday's now-cancelled meeting had been Iran's enrichment of uranium.

The United States, Israel and other Western countries have long accused Iran of seeking a nuclear weapon, an accusation it has categorically denied.

The huge wave of Israeli attacks on Iran's military and nuclear facilities on Friday has cast the future of the talks into doubt.

A US administration official told AFP on condition of anonymity that "while there will be no meeting Sunday, we remain committed to talks and hope the Iranians will come to the table soon".

Iranian President Masoud Pezeshkian said Tehran would not attend nuclear talks as long as Israel kept up its attacks.

In a call with his French counterpart Emmanuel Macron, Pezeshkian said Iran favoured diplomacy, but will not "accept irrational demands under pressure or... sit at the negotiating table while the Zionist regime continues its attacks", according to a readout shared by the Iranian presidency.

Macron said in a post on X that he had asked Pezeshkian to "return swiftly to the negotiating table".