As Iran mourns the death of one of its most revered Army General Qassem Soleimani, US President Donald Trump doubled down on Sunday on a threat to attack Iranian cultural sites despite accusations that any such strike would amount to a war crime. After his top diplomat, Mike Pompeo, had insisted that any military action would conform to international law, Trump said he would regard cultural sites as fair game if Iran resorted to deadly force against US targets.

“They’re allowed to kill our people, they’re allowed to torture and maim our people, they’re allowed to use roadside bombs and blow up our people and we’re not allowed to touch their cultural site? It doesn’t work that way,” Trump told reporters.

“If they do anything there will be major retaliation.” His comments on his return from a break in Florida followed a welter of criticism over a Tweet on Saturday night in which he said sites which were “important to… Iranian culture” were on a list of 52 potential US targets.

Iran is talking very boldly about targeting certain USA assets as revenge for our ridding the world of their terrorist leader who had just killed an American, & badly wounded many others, not to mention all of the people he had killed over his lifetime, including recently….

— Donald J. Trump (@realDonaldTrump) January 4, 2020

….targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD. The USA wants no more threats!

— Donald J. Trump (@realDonaldTrump) January 4, 2020

Tehran’s foreign minister had reacted to those initial comments by drawing parallels with the ISIS group’s destruction of the Middle East’s cultural heritage.

And as Twitter was flooded with photos of revered Iranian landmarks in ancient cities such as Isfahan under the hashtag #IranianCulturalSites, leading US Democrats said the president would be in breach of international protocols if he made good on his threat.

Targeting cultural sites is prohibited by international conventions signed in Geneva and at the Hague. In 2017, the United Nations security council passed unanimously a resolution condemning the destruction of heritage sites. The action previewed by Trump would almost certainly involve the deaths of civilians.

“You are threatening to commit war crimes,” Senator Elizabeth Warren, one of the top Democrats hoping to challenge Trump in November’s election, wrote on Twitter.

You are threatening to commit war crimes. We are not at war with Iran. The American people do not want a war with Iran. This is a democracy. You do not get to start a war with Iran, and your threats put our troops and diplomats at greater risk. Stop. pic.twitter.com/RoXRgb9GsK

— Elizabeth Warren (@ewarren) January 5, 2020

“We are not at war with Iran. The American people do not want a war with Iran.”

“Targeting civilians and cultural sites is what terrorists do. It’s a war crime,” added fellow Senator Chris Murphy.

Targeting civilians and cultural sites is what terrorists do. It’s a war crime.

Trump is stumbling into a war of choice. A war entirely of his making. A war that will get thousands of Americans killed.

Congress must stop him. https://t.co/446VOGmeZW

— Chris Murphy (@ChrisMurphyCT) January 5, 2020

In a flurry of interviews on the Sunday talk shows, Secretary of State Pompeo said the US would not hesitate to hit back hard against Iran’s “kleptocratic regime” if it came under attack, but pledged that any action would be consistent with the rule of law.

Both sides have traded threats since a US drone strike in Iraq on Friday killed Qassem Soleimani, one of the most important figures in the Iranian government. “We’ll behave lawfully. We’ll behave inside the system. We always have and we always will,” Pompeo told the ABC network.

“The American people should know that every target that we strike will be a lawful target, and it will be a target designed with a singular mission, of protecting and defending America.”

His comments came after his counterpart in Tehran Mohammad Javad Zarif tweeted that “targeting cultural sites is a WAR CRIME”.

-Having committed grave breaches of int’l law in Friday’s cowardly assassinations, @realdonaldtrump threatens to commit again new breaches of JUS COGENS;

-Targeting cultural sites is a WAR CRIME;

-Whether kicking or screaming, end of US malign presence in West Asia has begun.

— Javad Zarif (@JZarif) January 5, 2020

“A reminder to those hallucinating about emulating ISIS war crimes by targeting our cultural heritage: Through MILLENNIA of history, barbarians have come and ravaged our cities, razed our monuments and burnt our libraries,” said Foreign Minister Zarif. “Where are they now? We’re still here, & standing tall.”