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.

Russian President Vladimir Putin has proposed holding “direct talks” with Ukraine on Thursday in Istanbul, as European leaders and the United States attempt to put pressure on Moscow to agree to a 30-day ceasefire in order to bring an end to the three-year conflict.

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.