Iran said it was tightening control over the Strait of Hormuz on Saturday, warning mariners that the energy lifeline was again closed, as shipping sources said at least two vessels reported coming under fire while trying to transit the waterway.
Tehran said it was responding to a continued US blockade of Iranian ports, calling it a violation of their ceasefire, while Supreme Leader Mojtaba Khamenei, in hiding since his promotion, said Iran's navy was ready to inflict "new bitter defeats" on its enemies, despite being completely or almost completely destroyed.
Tehran’s renewed tough messaging injected fresh uncertainty around the Iran conflict, raising the risk that oil and gas shipments through the Strait could remain disrupted just as Washington weighs whether to extend the fragile ceasefire.
Some merchant vessels received radio messages from Iran’s navy saying no ships were allowed through the waterway, maritime security and shipping sources said, reversing signs earlier in the day that traffic might resume.
At least two vessels reported being hit by gunfire as they attempted to cross the strait, the sources said.
Earlier, maritime trackers had shown a convoy of eight tankers transiting the narrow passage in the first major movement of ships since the US-Israeli war on Iran began seven weeks ago.
Hours earlier, US President Donald Trump had cited "some pretty good news" about Iran, declining to elaborate. But he also said fighting might resume without a peace deal by Wednesday, when the two-week ceasefire expires.
Iran had announced its temporary reopening of the Strait of Hormuz following a separate US-brokered 10-day ceasefire agreement on Thursday between Israel and Lebanon. Israel invaded parts of southern Lebanon after the Iran-allied Hezbollah militant group joined the fighting in early March.
But on Saturday Iran's armed forces command said transit through the strait had reverted to a state of strict Iranian military control, citing what it described as repeated US violations and acts of “piracy” under the guise of a blockade.
The spokesperson said Iran had earlier agreed “in good faith” to the managed passage of a limited number of oil tankers and commercial vessels following negotiations, but said continued US actions had forced Tehran to restore tighter controls on shipping through the strategic chokepoint.
US Central Command said in a statement that American forces were enforcing a maritime blockade of Iran, but did not comment on the latest Iranian actions.
The war with Iran, which began on February 28 with a US-Israeli attack on the Islamic Republic, has killed thousands, spread to Israeli attacks in Lebanon and sent oil prices surging because of the de facto closure of the strait.
Despite the initial movement of ships, Iran's deputy foreign minister, Saeed Khatibzadeh, said no date had been set for the next round of negotiations, adding that a framework of understanding must be agreed first.
Asked about reports Tehran had closed the strait, he said that the Americans had violated the terms of the ceasefire, and so, "there will be repercussions for them."
Trump has told Reuters there would probably be more direct talks between Iran and the US this weekend. Some diplomats said that was unlikely given the logistics of gathering in Islamabad, where the talks are expected to take place.
There were no signs of preparations early on Saturday for talks in the Pakistani capital, where the highest-level US-Iran negotiations since the 1979 Islamic Revolution ended without agreement last weekend.
The key Pakistani mediator, army chief Field Marshal Asim Munir, has concluded three days of talks in Tehran, the Pakistani military said. Pakistani Prime Minister Shehbaz Sharif was also returning to Islamabad after talks this week in Qatar, Saudi Arabia and Turkey.
A Pakistani source aware of mediation efforts said a meeting between Iran and the US could produce an initial memorandum of understanding, followed by a comprehensive peace agreement within 60 days.
Differences remained over Tehran's nuclear programme, which has been a sticking point in peace talks, with Iran defending its right to what it says is a civilian nuclear energy programme.
Trump told Reuters the US would remove Iran's stockpiles of enriched uranium. Iran's foreign ministry spokesperson told state TV the material would not be transferred anywhere.
Separately, a senior Iranian official said Tehran hoped a preliminary agreement could be reached in the coming days.
Oil prices fell about 10 per cent and global stocks jumped on Friday on the prospect of marine traffic resuming through the strait. Despite that, hundreds of vessels and about 20,000 seafarers remain stranded in the Persian Gulf awaiting passage through the waterway, shipping sources said.
At last weekend's talks, the US proposed a 20-year suspension of all Iranian nuclear activity, while Iran suggested a halt of three to five years, according to people familiar with the proposals.
Two Iranian sources have said there were signs of a compromise that could remove part of the stockpile.
(Reporting by Reuters bureaus, Writing by Raju Gopalakrishnan, William Maclean; Editing by William Mallard and Alex Richardson)