Keir Starmer has said he fears the Middle East is “on the brink” of all out war as he urged hundreds of Brits to leave Lebanon immediately.
The prime minister spoke as he prepares to address the United Nations General Assembly in New York for the first time since entering Downing Street.
Britain is also sending 700 troops to Cyprus in case an emergency evacuation from Lebanon takes place.
Hundreds have died in recent days as Israel has targeted Hezbollah militants in Lebanon.
Speaking to Radio Four’s Today programme, Starmer said he was “deeply concerned” about the increasing violence.
“We are potentially at a brink point and we have to come back from the brink,” he said.
“That’s why, with our allies, we have been very, very clear and co-ordinated in saying de-escalate. We need a ceasefire, we need to de-escalate, and that will be amongst the discussions I’ll be having in New York.”
On his plane to the US, the PM told reporters: “The most important message from me this evening is to British nationals in Lebanon, to leave immediately and I just want to reinforce that.
“Yes, we are ramping up the contingency plans, I think that you would expect that in light of the escalation.
“But it is important that we be really, really clear: now is the time to leave.
“More broadly, I am worried about the situation and I think we need to be clear we need de-escalation, we need a ceasefire, we need to pull back from the brink.
“I think that will be amongst the first topics we discuss in New York.”
Announcing the deployment of British troops to Cyprus on Tuesday night, defence secretary John Healey said: “Events in the past hours and days have demonstrated how volatile this situation is, which is why our message is clear, British nationals should leave now.
“We continue to urge all sides to step back from conflict to prevent further tragic loss of life.
“Our government is ensuring all preparations are in place to support British nationals should the situation deteriorate.
“I want to thank the British personnel who are deploying in the region for their commitment and professionalism.”