Britain will sustain or increase military support to Ukraine for as long as it takes, British Prime Minister Liz Truss has said.

"And that's why – at this crucial moment in the conflict – I pledge that we will sustain or increase our military support to Ukraine, for as long as it takes. New UK weapons are arriving in Ukraine as I speak – including more MLRS rockets. We will not rest until Ukraine prevails," Truss said, speaking at the UN General Assembly on Wednesday.