The two sides finalised a memorandum of understanding overnight, which will be signed in Switzerland on Friday.

The agreement has yet to be published, raising concerns about the outcome of previous sticking points such as Iran’s nuclear programme.

Talks on the fate of Tehran’s enriched uranium stockpile have been pushed into a second round of negotiations that will begin after the initial pact is signed in Geneva.

Speaking to The New York Times on the sidelines of his 80th birthday meal, Mr Trump suggested that the Islamic Republic could only enrich uranium to a certain level – a concession Iran already offered when the US president broke off negotiations in February and started the war.

He suggested in a separate interview that the US would remove Iran’s current stockpile but appeared relaxed about the timeline, saying it would take place “over the next month or two, there’s no rush” as the near weapons-grade material was “harmless”.

Mr Trump said that if Iran failed to agree nuclear terms, the US would restart the war and become “the guardian of the Middle East” in return for 20 per cent of the region’s oil revenues. He went on to praise Xi Jinping, China’s president, and Vladimir Putin, Russia’s president, for their help in reaching the settlement.

The US president announced that the deal had been agreed on Truth Social before he attended a UFC match on the south lawn of the White House, writing: “Ships of the World, start your engines. Let the oil flow!”

He said he expected the Strait of Hormuz to reopen on Friday after the area had been cleared of Iranian mines. Oil prices fell by around 4 per cent in early trading – the lowest price since March.