Palm Beach, Florida - President Donald Trump bizarrely claimed Monday that "regime change" was underway in Iran as the US holds peace talks with an unidentified alternative leader.

Trump's surprise announcement to reporters in Florida was short on detail about whom the US side had contacted, but he said it was "not the supreme leader," Mojtaba Khamenei.

He described the unidentified negotiator as "a top person" and "the most respected and the leader."

"We're going to get together today, by probably phone, because it's very hard to find a country – it's very hard for them to get out, I guess," Trump told reporters before boarding his plane.

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Trump was speaking shortly after he backed down from a threat to bombard Iran's power stations within the next day, an escalation Iran vowed would be met by reprisals at sensitive regional targets, further roiling the US and world economies.

Trump announced on his Truth Social site that he was allowing five days for talks.

But if talks don't produce results, he told reporters later, "we'll just keep bombing our little hearts out."

Trump claimed there were already "major points of agreement" with supposed negotiators, including on Iran end to any nuclear ambitions and giving up its enriched uranium stockpiles – all more or less things that Tehran had already agreed to before the US and Israel launched their unprovoked war.

The Republican also insisted that unidentified Iranian officials reached out under pressure of his threat to attack power stations.

"They called, I didn't call," he said. "They want to make a deal, and we are very willing to make a deal."

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Iranian media however said on Monday that there were no negotiations underway towards ending the war.

"There are no talks between Tehran and Washington," said Mehr news agency citing Iran's foreign ministry, adding that Trump's statements were part of a push "to reduce energy prices".

Earlier, Trump told AFP in a brief phone interview that "things are going very well."

Asked why he wouldn't identify the people talking to the US, Trump said "because I don't want them to be killed," in an apparent reference to Israel's tactics of assassinating leaders, often in order to prevent negotiations to end hostilities.