US secretary of state Antony Blinken and UK Foreign Secretary David Lammy have arrived in Kyiv.
Mr Lammy has described the trip as "the first joint visit of this kind for well over a decade".
The pair will attend a series of meetings with senior government officials including President Volodymyr Zelenskyy.
Their visit comes at a crucial time in the war, with Kyiv urging its allies to allow it to strike deeper into Russian territory with Western weapons.
Ukraine is expected to press even harder after Mr Blinken accused Iran yesterday of providing Russia with Fath-360 short-range ballistic missiles, a move which he called a "dramatic escalation" of the war.
