Boris Johnson has joined European leaders in a call for all sides to show restraint after the US assassination of Iranian general Qasem Soleimani.
In a joint statement with Germany’s Angela Merkel and France’s Emmanuel Macron they said the current cycle of violence “must be stopped”.
Johnson will meet key ministers later and has discussed the deepening crisis with US President Donald Trump.
Iran has vowed revenge after General Soleimani was killed in a US strike.
In the joint statement, issued on Sunday night, Johnson and his French and German counterparts urged restraint and called on Iran to refrain from further violent action and proliferation.
The three leaders said they were concerned by the “negative” role Iran has played in the region but called on “all parties to exercise utmost restraint and responsibility”.
With tensions rising in the region following the drone strike ordered by President Trump, Iran has responded by vowing revenge and announcing it will no longer abide by the restrictions in its 2015 nuclear deal.
In the statement, the three leaders urged the country to “reverse all measures inconsistent with” the deal.
Meanwhile, Johnson is preparing to assemble key ministers to discuss the spiralling crisis in the Middle East.
The prime minister said he spoke to Trump on Sunday about the assassination of the Iranian general, who spearheaded the country’s military operations in the Middle East as head of the elite Quds Force.
The White House said the two leaders had discussed the current situation and “reaffirmed the close alliance between the two countries”.