Volodymyr Zelenskyy will visit Downing Street on Thursday, as Europe waits on tenterhooks for Donald Trump's face-to-face meeting with Russian President Vladimir Putin on Friday.
Keir Starmer's meeting with the Ukrainian President comes a day after he warned that Britain stands ready to "increase pressure" on Russia if necessary.
Trump has likewise threatened Russia with "severe consequences" if a ceasefire is rejected by its leader.
During a call with the US president and European allies on Wednesday, Sir Keir praised Mr Trump for his work to bring forward a "viable" chance of an end to the war.
Concerns have been raised over the Ukrainian President's exclusion from Friday's meeting, which is set to take place in Alaska. European leaders have consistently stated that discussions aroun