United States President Donald Trump has said that negotiations with Tehran are set to begin on Monday after he decided to hold off on new strikes on Iran in pursuit of a deal.

Trump said on Sunday that a plan was in place for the US to launch “the biggest attack since World War II” against Iran but that he halted it to give diplomacy a chance.

“Obviously, they don’t want to be attacked. They knew the extent of the attack because they saw it forming,” Trump told reporters on board Air Force One on Sunday.

“Now what we’re doing is talking to them in the form of a negotiation. It begins tomorrow afternoon.”

He gave no details about the venue or participants in the talks.

Trump pulled back from threats of an attack on Saturday after saying the “perimeter” of a deal was in place.

In his latest comments, Trump said Iran and US partners Saudi Arabia, the United Arab Emirates and Qatar had urged him to hold off on the strikes.

“When the allies asked to call it off, you’ve got to sort of say, ‘Well, let’s see.’ And the reason they ask is they think there’s a deal,” he said.

“There’s a deal on [the Strait of] Hormuz, and then there will be a deal on the nuclear, or you might call it the denuclearisation of Iran.”

He said Saudi Arabia’s Crown Prince Mohammed bin Salman had also urged against the strikes, warning of possible unintended consequences.

“I mean, will they be flooded with people pouring into their country and disaster? A lot of bad things can happen,” Trump said.

Regional diplomacy intensifies

Trump’s announcement came hours after Iranian Minister of Foreign Affairs Abbas Araghchi held a second phone call with Saudi Foreign Minister Prince Faisal bin Farhan Al Saud, joined by Pakistani Army Commander Asim Munir, to discuss recent diplomatic efforts.

The officials exchanged views on the current situation and on “initiatives aimed at maintaining and strengthening security and stability” in West Asia, Araghchi said in a Telegram post. They also stressed the need to use regional cooperation and political solutions, he added.

Earlier on Sunday, Iran’s official news agency IRNA reported that negotiations between Tehran and Oman over the Strait of Hormuz were in their final stages, citing Araghchi.

Iranian Ministry of Foreign Affairs spokesperson Esmaeil Baghaei said the negotiations focused on agreeing to a new route through the strait, adding that this had “no link to the Strait of Hormuz being opened or closed. That is a separate discussion”.

The war began on February 28, when the US and Israel launched surprise strikes against Iran, although months of on-and-off diplomacy have led to periods of relative calm.

A previous ceasefire deal, which included the reopening of the Strait of Hormuz, a vital conduit for global energy supplies, fell through. Iran has since tightened its control over the waterway as the two countries resumed attacks against each other in recent weeks.

Oil prices fall as escalation fears ease

Oil prices dropped sharply in early trading after Trump abandoned plans for a new military operation against Iran, easing fears of further disruption to Gulf energy supplies.

Brent futures were down $4.08, or 4.64 percent, at $83.85 a barrel on Sunday. West Texas Intermediate lost $4.01, or 4.74 percent, to trade at $80.66, according to the Reuters news agency.

The decline reversed part of last month’s surge, when both benchmarks gained more than 20 percent as renewed US-Iran fighting and attacks on commercial vessels near Oman intensified concerns over shipping through the region.