Sir Keir Starmer has called on Russian president Vladimir Putin to accept an unconditional 30-day ceasefire in Ukraine starting on May 12.
The announcement was made on Saturday alongside leaders of France, Germany, Poland and Ukraine after a meeting in Kyiv, following a phone call with Donald Trump.
"All of us here, together with the US, are calling Putin out. If he is serious about peace, then he has a chance to show it," Mr Starmer told reporters at a news conference.
He added: “If Putin turns his back on peace, we will respond. We will ramp up sanctions and increase military support for Ukraine to pressure Russia back to the table.”
