The leaders of the United Kingdom, France, and Germany on Sunday called for “restraint and responsibility” following the US assassination of the Iranian military leader Qassem Soleimani.

In a joint statement, the leaders said the cycle of violence escalated by President Donald Trump “must be stopped.”

UK Prime Minister Boris Johnson was scheduled to meet with key ministers on Monday to discuss the UK’s response to the crisis.

Visit Business Insider’s homepage for more stories.

The leaders of the United Kingdom, France, and Germany have released a joint statement calling for the “utmost restraint and responsibility” after President Donald Trump threatened to hit Iran “very fast and very hard.”

In a statement issued by UK Prime Minister Boris Johnson, German Chancellor Angela Merkel, and French President Emmanuel Macron on Sunday, the leaders said there was an “urgent need for de-escalation” and insisted the current cycle of violence “must be stopped.”

Addressing Iran’s announcement that it would no longer abide by the terms of the 2015 nuclear deal, formally known as the Joint Comprehensive Plan of Action, the statement added: “We specifically call on Iran to refrain from further violent action or proliferation, and urge Iran to reverse all measures inconsistent with the JCPOA.”

Iran has vowed to seek revenge after Maj. Gen. Qassem Soleimani, one of the country’s most powerful figures, was killed in a US airstrike in Iraq last week that was personally ordered by Trump.

Trump threatened to target 52 Iranian sites, however, should Iran retaliate. Among the sites, he said, were culturally significant landmarks.

….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! Lees ook op Business Insider In vrijwel de gehele Randstad moeten horecazaken vanwege het oplopende aantal coronabesmettingen om uiterlijk 1 uur sluiten — Donald J. Trump (@realDonaldTrump) January 4, 2020

While attacking such sites would constitute a war crime under both the Geneva and Hague conventions, Trump risked further inflaming tensions on Sunday when he doubled down on his aggressive rhetoric.

“They’re allowed to kill our people,” he told reporters. “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 sites? It doesn’t work that way.”

Johnson on Monday morning was expected to gather his most senior ministers, including Foreign Secretary Dominic Raab and Defense Secretary Ben Wallace, as they scrambled to navigate a response to the crisis.

The UK faces the difficult task of talking Trump down from his aggressive position without explicitly condemning Washington’s actions.

The prime minister said he spoke with Trump on Sunday about the death of Soleimani, who spearheaded Iran’s military and covert operations in the Middle East and was seen as perhaps the country’s most capable military figure.

The White House said the two leaders had discussed the situation and “reaffirmed the close alliance between the two countries.”

Earlier Sunday, Johnson said the general had been “responsible for a pattern of disruptive, destabilizing behavior in the region.”

“Given the leading role he has played in actions that have led to the deaths of thousands of innocent civilians and western personnel, we will not lament his death,” Johnson said.

“It is clear, however, that all calls for retaliation or reprisals will simply lead to more violence in the region and they are in no one’s interest.”