President Donald Trump has suggested the United States will destroy Iranian “civilisation” if Tehran does not open the Strait of Hormuz and submit to his terms.

About 12 hours before the Tuesday night deadline he set for Iranian authorities, Trump shared a social media post threatening to irreversibly obliterate Iran.

“A whole civilisation will die tonight, never to be brought back again. I don’t want that to happen, but it probably will,” Trump wrote on his Truth Social platform.

Iran is the heir to the millennia-old Persian civilisation, one of the most influential in human history.

For more than two weeks, the US president has been warning that he would order the destruction of Iran’s civilian infrastructure, including bridges and power stations, if his demands are not met.

His latest post on Tuesday reflected the escalating and angry rhetoric he has deployed since the US and Israel launched the war on Iran on February 28.

Legal experts said targeting civilian infrastructure is a war crime.

“It’s horrific. It’s pure evil. It’s disqualifying,” Yasmine Taeb, legislative and political director for the advocacy group MPower Change Action Fund, said of Trump’s threats.

“It’s the words of a deranged, unstable madman.”

Taeb called for a “stronger reaction” from US lawmakers and the international community against Trump’s rhetoric and policies.

Democrats call for ending war

Several Democratic members of the US Congress on Tuesday condemned Trump’s threats and called for ending the war.

Chuck Schumer, the top Democrat in the Senate, called Trump an “extremely sick person” after the president’s post on Tuesday.

“Each Republican who refuses to join us in voting against this wanton war of choice owns every consequence of whatever the hell this is,” the senator wrote on X.

Hakeem Jeffries, the top Democrat in the House of Representatives, called on legislators from Trump’s Republican Party to “put patriotic duty over party and stop the madness.”

“Congress must immediately end this reckless war of choice in Iran before Donald Trump plunges us into World War III,” Jeffries said in a social media post.

Last month, Congress failed to pass a resolution to curb Trump’s powers to attack Iran.

The US president has not obtained authorisation from lawmakers to launch the military campaign against Iran in what critics said is a violation of the US Constitution, which grants Congress the power to declare war.

On Tuesday, Congresswoman Rashida Tlaib said the 25th Amendment of the constitution should be invoked to remove Trump from office because he is unfit to serve.

“After bombing a school and massacring young girls, the war criminal in the White House is threatening genocide,” Tlaib wrote in a social media post, referring to the Minab school attack in southern Iran that killed more than 170 people.

Congressman Jim McGovern stressed that the US military is required to disobey “illegal orders”.

“This is evil. The President of the United States’ genocidal threat to commit war crimes is illegal under federal & international law,” McGovern said.

Despite the intensifying opposition to the war on the Democratic side, dissent against Trump has remained faint among Republicans.

On Tuesday, Congressman Mike Lawler played down Trump’s threat to kill off Iran’s civilisation, saying the president would target only the country’s civilian infrastructure.

“It is their energy infrastructure and their civilian infrastructure, including roads and bridges. That will cripple the Iranian regime and certainly their economy,” Lawler told CNN.

The Republican lawmaker said Trump is acting “within his legal authorities to conduct this war” as commander-in-chief of the US armed forces.

The deadline

The US president set 8pm in Washington, DC, (00:00 GMT) on Tuesday as the “final” deadline for Iran.

On the first day of the war, the US and Israel killed Iranian Supreme Leader Ali Khamenei and several other top officials.

The attacks have killed more than 2,000 people and hit schools, residential buildings and medical facilities.

Despite the losses, the governing system in Tehran appears to have held together with the Islamic Revolutionary Guard Corps – a wing of the Iranian military that is designated as a “terrorist” group in the US – spearheading the war effort.

There have been no major defections or antigovernment protests in Iran since the start of the war, and Khamenei was replaced by his son Mojtaba.

Iran has retaliated with rocket and drone attacks against Israel and US assets across the entire Middle East.

Iranian forces have also targeted civilian and energy infrastructure in the Gulf region and blocked the Strait of Hormuz to most shipping, sending energy prices soaring.

Still, Trump has insisted that he achieved “regime change” in Iran and the US has “won” the war.

On Tuesday, Trump left the door open for a diplomatic resolution despite his dramatic threat, saying “maybe something revolutionarily wonderful can happen.”

“We will find out tonight, one of the most important moments in the long and complex history of the World. 47 years of extortion, corruption, and death will finally end. God Bless the Great People of Iran!” Trump wrote.

Iranian officials have remained defiant, threatening to meet any US escalation with similar military measures in the region and beyond.

Later on Tuesday, US Vice President JD Vance also issued a warning to Iran, saying that the US wants oil and gas to flow “freely”.

“They’ve got to know, we’ve got tools in our toolkit that we so far haven’t decided to use,” he said during a speech in Hungary. “The president of the United States can decide to use them, and he will decide to use them if the Iranians do not change their course of conduct.”