The wildly provocative statement -- the latest in a recent torrent of strident language by Trump -- prompted swift and severe criticism, with one of his former close allies calling for his removal from office.

Vice President JD Vance offered his own threatening assessment of what may follow, warning Tehran that US forces have tools they "so far haven't decided to use" against the Islamic republic.

Since February 28 the United States and its ally Israel have leveled Iranian military targets, killed the country's top leadership and devastated parts of its infrastructure.

Early Tuesday Trump issued one of his most glaring threats of the war.

"A whole civilization will die tonight, never to be brought back again. I don't want that to happen, but it probably will," he wrote on his Truth Social platform.

Trump did not give details but he has already said the US military could bomb Iran's bridges, power plants and other civilian infrastructure into the "stone age."

Trump has announced a deadline of midnight GMT Tuesday for Iran to end its de facto closing of the Strait of Hormuz, a narrow, strategic waterway used to transport oil and other commodities.

On Monday, he said a temporary ceasefire proposal being circulated was insufficient.

Iran has rejected US pressure, with state media reporting authorities are insisting that instead of a ceasefire it wants a full end to the war.

- 'Sick beyond measure' -

On Truth Social, Trump left the door open for a last-hour agreement.

"Now that we have Complete and Total Regime Change, where different, smarter, and less radicalized minds prevail, maybe something revolutionarily wonderful can happen, WHO KNOWS? We will find out tonight," he wrote.

Trump said Monday that starting in Washington late Tuesday evening, US forces would destroy "every bridge in Iran" and cripple "every power plant" -- something many experts say would be a blatant war crime.

The extent of Trump's saber rattling and goading language has appalled critics.

"These are the rantings of a bloodthirsty lunatic. It is sick beyond measure to threaten to wipe out an entire civilization," said longtime Democratic Senator Patty Murray, one of several lawmakers to lash out at Trump.

"This is not what the American people want. It is well past time for the Republican Congress to join Democrats and put an end to this war."

Even some political figures once close to Trump are calling for his removal through the US Constitution's 25th Amendment, which provides for a transfer of power if a president is unable to govern, particularly in the event of illness.

"25TH AMENDMENT!!! Not a single bomb has dropped on America," former congresswoman Marjorie Taylor Greene wrote on X. "We cannot kill an entire civilization. This is evil and madness."

Anthony Scaramucci, a financier who briefly worked in Trump's White House, urged Republicans to "wake up" because the president "is calling for A NUCLEAR STRIKE. Seek his removal immediately."

Meanwhile Vance, visiting Hungary, delivered an ominous warning to Iran.

"They've got to know we've got tools in our toolkit that we so far haven't decided to use," Vance said. Trump "will decide to use them if the Iranians don't change their course of conduct."

Team Trump denied Vance's remarks contained any suggestion of nuclear attack.

"Literally nothing @VP said here 'implies' this, you absolute buffoons," the White House said on X.

The post was in response to one from an account associated with Kamala Harris, which said Vance implied Trump "might use nuclear weapons."