Boris Johnson has called for the "cycle of violence" in Iraq to be stopped, after an Iranian general was killed in a US air strike.
The Prime Minister said that he would not "lament" the death of Qasem Soleimani in the strike ordered by Donald Trump, but said there was an "urgent need for de-escalation".
In a joint statement along with his French and German counterparts Emmanuel Macron and Angela Merkel, Mr Johnson said: "We call on all parties to exercise utmost restraint and responsibility. The current cycle of violence in Iraq must be stopped.
"We specifically call on Iran to refrain from further violent action or proliferation, and urge Iran to reverse all measures inconsistent with the JCPOA (the Iran nuclear deal).
"We recall our attachment to the sovereignty and security of Iraq. Another crisis risks jeopardising years of efforts to stabilise Iraq.
"We also reaffirm our commitment to continue the fight against Daesh (Islamic State), which remains a high priority. The preservation of the Coalition is key in this regard. We therefore urge the Iraqi authorities to continue providing the Coalition all the necessary support.
"We stand ready to continue our engagement with all sides in order to contribute to defuse tensions and restore stability to the region."
Sixty-two-year-old Soleimani was head of Iran's Quds Force and was killed at Baghdad airport.
Mr Trump said the general was "responsible for the deaths of millions of people".