US President Donald Trump has said new talks with Iran will begin on Monday, after calling off what he said would have been "massive" strikes on the country.

"They knew the extent of the attack because they saw it forming," he told reporters on board Air Force One on Sunday. "We're talking to them in the form of a negotiation. It begins tomorrow afternoon."

In an earlier post on Truth Social, Trump said he had been asked by Iran and US allies in the Middle East to "hold off" on any attack as the "perimeters" of a deal had been agreed.

Iran's foreign ministry said there are no plans to receive a US delegation or send Iranians to Washington. Earlier talks have been facilitated through mediators.

The US president has repeatedly vowed that a negotiated end to the war is near, only for tit-for-tat strikes to resume.

In his remarks on Air Force One, Trump declined to outline a deadline for a deal to be struck with Tehran, adding: "We'll just see how it is. We're ready to go anytime we want... I'm not looking to kill people."

Trump added that Saudi Arabia's Crown Prince Mohammed Bin Salman - as well as US partners such as the United Arab Emirates and Qatar - had urged him against conducting strikes over the weekend.

"We were all set to go," Trump said. "The reason they asked is [that] they think there's a deal," he said. "There's a deal on Hormuz, and there will be a deal on the nuclear."

Global oil prices fell on Monday morning in Asia trading after Trump's announcement. Brent Crude oil was down by 4.5% at $83.98 (£62.26), while US-traded oil was 4.6% lower at $80.74 (£59.85).

Energy prices have fluctuated since the conflict started on 28 February as traders reacted to disruptions to shipping through the Strait of Hormuz.

Around 20% of the world's crude oil and liquefied natural gas (LNG) usually flows through the strait.

Iran's semi-official Mehr news agency denied that Tehran had asked the US to hold off on further military action, saying Trump's claims were "nothing but a new lie".

On Sunday, Iranian Foreign Minister Abbas Araghchi said that negotiations with Oman on a deal on the Strait of Hormuz were "on track for finalisation", according to Iranian media.

The US president has not yet made clear the venue for the talks on Monday, nor the potential attendees.

During his remarks on Air Force One, Trump said that the planned strikes would have been "the biggest attack since World War II", and could have derailed prospects of a negotiated end to the months-long war.

Trump declined to answer if he had been planning to strike Iranian energy infrastructure, which international law experts have said could constitute a war crime.

Iran's acting Defence Minister Majid Ibn al-Reza earlier said Tehran viewed every threat from its adversaries as "real and credible" even if it formed part of psychological warfare.

"We will neither be caught off guard nor remain passive," he added.