Ministers from France, Germany, Italy, Poland, Spain and the EU joined the UK Foreign Secretary David Lammy for a meeting of the so-called "Weimar+" group,
France 24 reports.
The meeting follows Saturday's visit by the leaders of France, Germany, Poland and the UK to Kyiv, where they called for "a full, lasting and reliable" 30-day ceasefire from Monday, as a condition for opening direct talks.
"This is the time for Vladimir Putin to get serious about peace in Europe, to get serious about a ceasefire and to get serious about talks," Lammy said on Monday.
He warned that European countries must "be prepared if this is not the moment of seriousness from Putin and we do not get that peace".
The "Weimar+" group was set up in February in response to shifting US policy towards the war in Ukraine and European security under President Donald Trump.
The EU's top diplomat Kaja Kallas renewed calls for a ceasefire on Monday.
"If there is no ceasefire there cannot be talks under fire," she said in London, accusing Russia of "playing games".
"It takes two to want peace. It takes only one to want war. And we see that Russia clearly wants war," she added.
