Britain's foreign minister will host European peers on Monday to discuss support for Ukraine and greater regional defence cooperation in the run-up to Prime Minister Keir Starmer's summit with European Union leaders next week.
UK Foreign Secretary David Lammy was due to hold talks with representatives of France, Italy, Germany, Spain, Poland and the EU, Britain's foreign ministry said.
"We are facing a once-in-a-generation moment for the collective security of our continent," Lammy said in a statement. "The challenge we face today is not only about the future of Ukraine - it is existential for Europe as a whole."
Lammy planned to announce further sanctions targeting actors supporting Russia's invasion of Ukraine, the statement said.
The leaders of Britain, France, Germany and Poland travelled to Kyiv on Saturday to back Ukraine's call for an unconditional 30-day ceasefire on Saturday, with the backing of U.S. President Donald Trump.
They also threatened President Vladimir Putin with "massive" new sanctions if he did not accept within days. Putin on Sunday proposed direct talks with Ukraine aimed at ending the war.
Lammy would use Monday's meeting to press Britain's calls for a strengthening of European security, the ministry said.
At a summit with EU leaders on May 19, Starmer is hoping to clinch a new defence agreement with the bloc and improve post-Brexit trade ties following Trump's upending of security and trade alliances.
