As mediation efforts continued following high-level talks in Pakistan that failed to reach a deal, Iran said it would not reopen the crucial maritime trade route until the United States ended its blockade of Iranian ports.

Mohammad Bagher Ghalibaf, speaker of the Iranian parliament, said in a televised address on Saturday night that there had been "progress" with Washington "but there are many gaps and some fundamental points remain".

"We are still far from the final discussion," said Ghalibaf, one of Tehran's senior negotiators in the talks aimed at ending the war launched by Israel and the United States against the Islamic republic.

A two-week ceasefire is set to end on Wednesday unless it is renewed.

US President Donald Trump said "very good conversations" were going on with Iran but warned Tehran against trying to "blackmail" the United States.

On Friday, Tehran had declared the Strait of Hormuz, through which a fifth of the world's oil and liquefied natural gas usually transits, open after a temporary ceasefire was agreed to halt Israel's war with Iran's ally Hezbollah in Lebanon.

That prompted elation in global markets and sent oil prices plunging, but Tehran reversed course after Trump insisted the US blockade of Iranian ports would continue until a final deal was struck.

"If America does not lift the blockade, traffic in the Strait of Hormuz will definitely be limited," Ghalibaf said.

Trump accused Iran of getting "a little cute" with its recent moves and warned Tehran not to try to "blackmail" Washington by flip-flopping on the strait.

"We have very good conversations going on," the president told reporters at the White House, adding that the United States was "taking a tough stand".

- 'Targeted' -

Iran's Revolutionary Guards warned that any attempt to pass through the strait without permission "will be considered cooperation with the enemy, and the offending vessel will be targeted".

A handful of oil and gas tankers crossed the strait early on Saturday during the brief reopening, tracking data showed, but others retreated and hardly any vessels were crossing by the late afternoon.

On Sunday morning, the entrance to the Gulf appeared to be at a standstill, with tracking data showing the strait itself empty of shipping.

The day before, a trio of incidents demonstrated the dangers of any attempted crossing.

A UK maritime security agency said the Revolutionary Guards fired at one tanker, while security intelligence firm Vanguard Tech reported the force had threatened to "destroy" an empty cruise ship that was fleeing the Gulf.

In the third incident, the UK agency said it received a report of a vessel "being hit by an unknown projectile, which caused damage" to shipping containers but no fire.

The Indian foreign ministry said it had summoned the Iranian ambassador to lodge a protest over a "shooting incident" involving two Indian-flagged ships in the strait.

- 'Nuclear rights' -

On the diplomatic front, Egypt, which has been involved in mediation efforts with Pakistan, appeared optimistic on Saturday, with Foreign Minister Badr Abdelatty saying Cairo and Islamabad hoped to secure a final agreement "in the coming days".

A major sticking point has been Iran's stockpile of near-weapons-grade enriched uranium.

Trump said Friday that Iran had agreed to hand over its roughly 440 kilogrammes of enriched uranium. "We're going to get it by going in with Iran, with lots of excavators," he said.

Iran's foreign ministry has said the stockpile, thought to be buried deep under rubble from US bombing in last June's 12-day war, was "not going to be transferred anywhere" and surrendering it "to the US has never been raised in negotiations".

On Sunday, President Masoud Pezeshkian questioned why Iran should give up its "legal right" to a nuclear programme.

"How come the US president declares that Iran should not use its nuclear rights but does not say why?" said a statement from the Iranian presidency.

"How in the world is he trying to deprive a nation of its legal rights?"

The Middle East war was started on February 28 by a massive wave of US-Israeli attacks on Iran, despite Washington and Tehran being engaged in negotiations at the time.

The conflict rapidly spread across the region, with Iran targeting neighbouring Gulf countries that are home to US military bases, and Iran-backed Hezbollah dragging Lebanon into the war by launching rockets at Israel.

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