Donald Trump issued an expletive-laden warning on Sunday that Tehran had until Tuesday night to reopen the strait of Hormuz or the US would obliterate Iran’s power plants and bridges.

Iran’s powerful parliament speaker responded with a warning that the US president’s “reckless moves” would mean “our whole region is going to burn”.

The latest threat of escalation in the five-week-old war followed the rescue of a second crew member of a downed F-15E fighter by US commandos, ending a two-day search after the warplane crashed in south-west Iran.

Iran distributed images showing the wreckage of several aircraft, but did not deny that US forces had rescued the officer who had taken cover in a mountainous area while American special forces and Iranian troops raced to find him.

Trump has extended deadlines at least twice for Iran to reopen the strait of Hormuz, which has sent the price of oil shooting up, and shifted his deadline again from Monday to Tuesday in his expletive-laden post.

“Tuesday will be Power Plant Day, and Bridge Day, all wrapped up in one, in Iran. There will be nothing like it!!! Open the Fuckin’ Strait, you crazy bastards, or you’ll be living in Hell – JUST WATCH! Praise be to Allah. President DONALD J. TRUMP”, the US president posted on his Truth Social website.

Trump separately suggested that there is a “good chance” of an agreement with Iran on Monday, telling Fox News that negotiations were taking place. “If they don’t make a deal and fast, I’m considering blowing everything up and taking over the oil,” he said.

However, Trump has repeatedly said since the US-Israeli war started on 28 February that Iran wants to make a deal.

Iran has acknowledged that messages have been passed between the two sides, including through Pakistan. But Tehran insists that it has not entered into peace talks. Iranian officials also fear that they will be targeted when they break cover to head to any negotiations, according to diplomatic intermediaries.

Mohammad-Bagher Ghalibaf, the speaker of the Iran parliament, responded to Trump’s latest threats in a social media post. “Your reckless moves are dragging the United States into a living HELL for every single family, and our whole region is going to burn because you insist on following Netanyahu’s commands,” he wrote.

“Make no mistake: You won’t gain anything through war crimes. The only real solution is respecting the rights of the Iranian people and ending this dangerous game.”

Trump’s expletive-laden post also drew criticism on Capitol Hill.

“Happy Easter, America. As you head off to church and celebrate with friends and family, the President of the United States is ranting like an unhinged madman on social media,” the Democratic Senate minority leader, Chuck Schumer, said on X.

“He’s threatening possible war crimes and alienating allies. This is who he is, but this is not who we are. Our country deserves so much better.”

The destruction on Thursday of the region’s tallest bridge, hailed in Iran as an engineering marvel, pointed to a grim new phase of the war, in which the US president has threatened to throw Iran back to the “stone ages”.

During war, international law protects civilians and what are known as civilian objects, such as infrastructure, rules that are enshrined in the Geneva conventions.

Oona A Hathaway, a professor of international law at Yale University, said that US president had offered no explanation that would make the civilian objects he has threatened to target into lawful military objectives. She also warned that other nations had an obligation to ensure respect of the Geneva conventions, and not to aid and abet wrongful acts.

“If these threatened attacks were to be carried out, they would constitute war crimes,” said Hathaway. “Immiserating the civilian population for bargaining leverage is not lawful.”

Iranian steel manufacturing sites, petrochemicals plants, universities and medical facilities have all been bombed during the joint US-Israeli campaign. About 81,000 civilian sites have been damaged, including 61,000 homes, 19,000 commercial sites, 275 medical centres, and nearly 500 schools, according to Iranian authorities.

The Israeli prime minister, Benjamin Netanyahu, has said Israel has destroyed 70% of Iran’s steel production, claiming it was used for making missiles. He has also confirmed attacks on petrochemical plants.

Iran has been able to take control of the strait of Hormuz by threatening and attacking shipping passing through the waterway, providing a chokehold on the oil trade that is Tehran’s strongest pressure point in the conflict.

Iran continued to hit economic infrastructure across the Gulf over the weekend in response to the attacks, in acts that legal experts have also said are unlawful. On Sunday, it struck a petrochemicals complex in Bahrain. Video footage showed thick black smoke rising from the site.

The Kuwait Petroleum Corporation said a number of its facilities were targeted by Iranian drone attacks, resulting in fires and “significant material losses”. Kuwait also reported that two power and water desalination plants sustained “significant material damage” after being attacked by Iranian drones.

In Lebanon, Israel again struck in southern Beirut, killing at least four people and injuring 39 others. Lebanon’s national news agency reported that an Israeli airstrike on southern Lebanon’s Kfar Hatta killed at least seven people, including a four-year-old girl.

It was on Thursday that Iranians got a visceral demonstration of the kinds of attacks that may now be unleashed, with the destruction of the 136 metre-high $400m (£300) B1 suspension bridge between Tehran and Karaj.

The attack happened on the last day of the holidays to mark Iranian new year, and according to reports many families were picnicking nearby when missiles punched through the middle of the bridge, sending up a giant fireball.

The day trippers, who had pitched tents to enjoy the holiday, ran screaming. Local authorities said that 13 people were killed and 95 injured in the attack.

The bridge had not even been opened. It was so far known only as B1, ahead of an inauguration due in the summer.

Trump posted a video of the bridge’s demolition, warning Iran to cut a deal before there was nothing left. On Sunday, Trump told Axios that several days ago, the US and Iran were close to an agreement to hold direct negotiations.

“But then they said they will meet us in five days. So I said, ‘Why five days?’ I felt they were not being serious. So I attacked the bridge.”

An engineer behind the bridge’s construction, interviewed on Iranian television, broke down. “We made everything with our own knowhow, workers and resources,” he said, using a tissue to wipe tears. “I am ashamed of myself for not being able to have people use it.”

A civil engineer in Iran who worked on other major infrastructure projects said that recent strikes on civilian infrastructure, all built with indigenous knowledge, had already “made it impossible to conceal hostility toward the Iranian people behind the mask of mere opposition to the government”. But it was the strike on the bridge that was most painful for him, as he said it had no military, nuclear or government link.

“The target of this attack was nothing other than Iran’s pride,” he said. “A nation that has achieved such a level of self-sufficiency and productivity cannot be returned to the stone age.”