Iran had offered a different timeline earlier in the day, but nonetheless signalled an agreement was in the offing, as both the warring parties and their mediators expressed increasing optimism that weeks of talks were drawing to a close.

"The Deal is scheduled to get signed tomorrow, and immediately after it is signed, the Hormuz Strait is OPEN TO ALL," Trump wrote on social media on Saturday.

The leader of key mediator Pakistan also said earlier that a deal was closer "than ever".

The "finalisation" of this agreement is expected "within the next 24 hours", Pakistani Prime Minister Shehbaz Sharif said Saturday on X, adding that it will be signed electronically.

He said "technical level talks" were expected to follow next week.

A Pakistani foreign ministry statement also said the signing was planned for Sunday.

But Iran's Fars news agency, citing "a well-informed source close to the Iranian negotiating team", reported that Tehran had "not yet taken or announced its final decision" on a deal.

Since an April 8 truce paused the worst of the fighting, Trump has repeatedly insisted a deal was imminent, only for the wrangling to drag on.

Iranian foreign ministry spokesman Esmaeil Baqaei however said earlier on Saturday that the date of the signing was yet to be determined, but "it will not be tomorrow".

However, he added: "The possibility of this happening in the coming days cannot be ruled out."

The warring parties have released conflicting information about the contents of the deal, as each seeks to show it emerged from the war with the upper hand.

A delegation from fellow mediator Qatar, meanwhile, arrived in Tehran on Sunday for talks, according to Iranian media.

Iran's ISNA news agency reported that an adviser to Qatar's foreign minister had been dispatched to the Islamic republic, while the Tasnim news agency said the visit's purpose was to "go over the latest developments regarding the diplomatic process".

- Hormuz drones -

Tehran has insisted it will maintain control over the Strait of Hormuz, a key maritime trade route for oil and gas shipments from the Gulf.

Since imposing its blockade on the strait -- which has thrown global markets into turmoil -- Iran has demanded vessels obtain permission from its armed forces before transiting the waterway, and has established a new body to oversee it and collect tolls.

The US has responded with its own blockade of Iranian ports.

The US military's Central Command said Saturday that Iran had "launched multiple one-way attack drones in an attempt to strike commercial ships transiting the Strait".

It added that "US forces have downed all of them in recent hours".

Iran's Foreign Minister Abbas Araghchi had said on Friday that the deal on the table called for the lifting of the US naval blockade.

"The administration of Strait of Hormuz will no longer be the same as before," he added, calling the waterway one of Iran's "main instruments of deterrence".

The US has repeatedly said Iran remaining in control of the strait would be unacceptable, and Trump's post made no mention of tolls or other arrangements.

- 'Nuclear dust' -

Another key sticking point in the talks has been the fate of Iran's nuclear programme, particularly its stockpile of highly enriched uranium -- believed to have been buried by US strikes last year.

Iran has long insisted its nuclear programme is peaceful and that it has a right to enrichment, but the US, Israel and other Western governments suspect it of seeking a bomb.

Araghchi on Friday said the only way to deal with Iran's enriched uranium "is to dilute it inside Iran".

Trump, who has justified the war as necessary to prevent Iran from obtaining nuclear weapons, previously said the US would remove and destroy the uranium.

In Saturday's post, he said: "When all is calm, we will go in and get the Nuclear Dust... and downblend and destroy it, whether in Iran or the United States."

Prime Minister Benjamin Netanyahu of Israel -- which launched the war in tandem with the US in February -- said Trump had promised him any agreement would include the removal of the enriched nuclear material.

A senior US official said Friday that a proposed deal to end the war would also include Lebanon, where Israel has been attacking Iran-backed Hezbollah militants.

Lebanon was drawn into the Middle East conflict when Hezbollah fired rockets at Israel on March 2.

An April ceasefire in Lebanon was never observed, and the fighting has continued despite a new conditional truce deal announced last week after Lebanese-Israeli talks in Washington.

On Sunday, the Israeli military issued evacuation warnings for residents of 29 villages in southern Lebanon ahead of planned strikes.

It also reported that three drones, suspected to have been launched by Hezbollah, struck northern Israel on Sunday but caused no casualties.

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