UK Prime Minister Rishi Sunak has urged Iran to de-escalate tensions in the Middle East after a drone attack by Tehran-backed forces killed three US soldiers in Jordan.

“We are concerned and would urge Iran to continue to de-escalate tensions in the region…We absolutely condemn what has happened over the past couple of days,” Sunak said on Monday.

US President Joe Biden on Sunday vowed to retaliate against the attack, as lawmakers and former US officials expressed outrage at the deadly attack, which they see as an Iranian declaration of war.

Britain, the closest US ally in Europe, joined the United States this month in launching retaliatory strikes against Yemen’s Houthi forces, armed and supported by Iran. The Houthis have been attacking international maritime traffic in the Red Sea since mid-November, after Iran’s Supreme Leader Ali Khamenei called on Muslim countries to blockade Israel.

Sunak expressed his concern as the world expects an imminent US retaliatory attack possibly in Syria, Iraq or even at Iranian targets.

“We stand resolutely with our allies to bring stability and peace to the region…And that’s what we’ll continue to work towards,” the Prime minister said.