Major European powers threw their weight behind an unconditional 30-day Ukraine ceasefire on Saturday, with the backing of U.S. President Donald Trump, and threatened President Vladimir Putin with "massive" new sanctions if he did not accept within days.

The announcement was made by leaders of Britain, France, Germany, Poland and Ukraine after a meeting in Kyiv, and a phone call with President Trump.

The UK will on Monday host European ministers for "critical" talks on "repelling Russian aggression", two days after Ukraine's allies demanded that Moscow accept a ceasefire. The London meeting, where Lammy is expected to announce further sanctions targeting those backing Russia's invasion,