Last-minute ceasefire talks between the US and Iran looked uncertain on Tuesday as a two-week truce was set to expire and both countries warned that, without a deal, they were prepared to resume fighting.
US vice president JD Vance, expected to lead US negotiators if talks continue, called off a trip to Pakistan, a US official said.
And Iran said it had not decided whether to participate.
Pakistani leaders, including Prime Minister Shehbaz Sharif, worked intensively late on Tuesday to get both sides to agree to a second round of ceasefire talks, according to two officials who spoke on condition of anonymity because they were not authorised to speak to the media.
The ceasefire was set to expire on Wednesday.
Iranian Foreign Ministry spokesman Esmail Baghaei told Iran’s state TV there has been “no final decision” on whether to attend because of “unacceptable actions” by the US, apparently referencing its recent blockade in the Strait of Hormuz.
As Mr Vance put on hold traveling for more ceasefire talks, US President Donald Trump’s special envoy Steve Witkoff and son-in-law Jared Kushner were expected in Washington DC on Tuesday afternoon for consultations about how to proceed, said an official, who spoke on condition of anonymity to discuss internal administration deliberations.
The official cautioned that Mr Trump could change his mind on negotiating with Iran at any minute, and declined to predict what would happen if the current ceasefire expires without another meeting in Islamabad, but noted that Mr Trump retains options short of restarting airstrikes.
Both sides remain dug in rhetorically.
Mr Trump has warned that “lots of bombs” will “start going off” if there’s no agreement before the ceasefire deadline, and Iran’s chief negotiator said that Tehran has “new cards on the battlefield” that have not yet been revealed.
The ceasefire, which began April 8, could be extended if talks resume, though Mr Trump said in an interview Tuesday with CNBC: “Well, I don’t want to do that.”
“We don’t have that much time,” Mr Trump said, adding that Iran “had a choice” and “they have to negotiate”.
White House officials have said that Mr Vance would lead the American delegation, but Iran has not said who it might send.
Iranian state television on Tuesday broadcast a message saying that “no delegation from Iran has visited Islamabad … so far”.
Meanwhile on Tuesday, the US said its forces boarded an oil tanker previously sanctioned for smuggling Iranian crude oil in Asia.
The Pentagon said in a social media post that US forces boarded the M/T Tifani “without incident”.
The US military did not say where the vessel had been boarded, though ship-tracking data showed the Tifani in the Indian Ocean between Sri Lanka and Indonesia on Tuesday.
The Pentagon statement added that “international waters are not a refuge for sanctioned vessels”.
The US military on Sunday seized an Iranian container ship, the first interception under a blockade of Iranian ports.
Iran’s joint military command called the armed boarding an act of piracy and a violation of the ceasefire.
The US imposed the blockade to pressure Tehran into ending its stranglehold on the Strait of Hormuz, a key shipping lane through which 20% of the world’s natural gas and crude oil transits in peacetime.
Iran’s grip on the strait has sent oil prices soaring.
Brent crude, the international standard, was trading at close to 95 dollars (£70) per barrel on Tuesday, up more than 30% from February 28, the day that Israel and the US attacked Iran to start the war.
Before the war began, the Strait of Hormuz had been fully open to international shipping.
Mr Trump has demanded that vessels again be allowed to transit unimpeded.
European Union transportation ministers were meeting on Tuesday in Brussels to discuss how to protect consumers after the head of the International Energy Agency warned that Europe has “maybe six weeks” of jet fuel supplies remaining.
Over the weekend, Iran said that it had received new proposals from Washington, but also suggested that a wide gap remains between the sides.
Issues that derailed the last round of negotiations included Iran’s nuclear enrichment programme, its regional proxies and the strait.
Iranian parliament speaker Mohammad Bagher Qalibaf on Tuesday accused the United States of wanting Iran to surrender.
“We do not accept negotiations under the shadow of threats,” he wrote in an X post.
Pakistani officials have expressed confidence that Iran will also send a delegation to resume talks that mark the highest-level negotiations between the US and Iran since the 1979 Islamic Revolution.
The first round April 11 and 12 ended without an agreement.
