Morristown, New Jersey - President Donald Trump said on Sunday that talks with Iran over its nuclear program have made "serious progress," but added that the outcome remains uncertain.

"We've had some very, very good talks with Iran and I don't know if I'll be telling you anything good or bad over the next two days, but I have a feeling I might be telling you something good," he told reporters in New Jersey.

Trump, who has repeatedly threatened Tehran with war, said he still hoped a deal could be reached.

"I'd love that to happen because I'd love to see no bombs dropped and a lot of people dead," he added.

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Talks are being mediated by Oman, whose Foreign Minister Badr al-Busaidi said on X that there had been "some but not conclusive progress" in the fifth round of negotiations on Friday.

"We hope to clarify the remaining issues in the coming days," he added.

It remains unclear when the parties will meet again.

Washington wants Tehran to halt uranium enrichment entirely, viewing it as vital to preventing Iran from developing nuclear weapons.

Iran has rejected that demand but has signalled willingness to limit its program – which it insists is not aimed at gaining arms – and accept stricter inspections.