Keir Starmer has rejected Vladimir Putin’s demand for countries to stop providing Ukraine with military aid.
A spokesman for the prime minister said the UK would continue to support Kyiv “for as long as it takes”.
Putin has said all foreign military and intelligence support for Ukraine must end before Russia will agree to a peace deal to end the war.
He outlined his terms during a phone call with Donald Trump on Tuesday.
Asked today for Starmer’s response to Putin’s demand, the PM’s official spokesman said: “We will always continue to support Ukraine militarily for as long as it takes to put Ukraine in the strongest position possible.”
During his call with Trump, Putin did agree to stop targeting Ukrainian energy plants for 30 days, but stopped well short of agreeing to a complete truce.
According to the Kremlin, he told the US president that he wanted a “complete cessation of foreign military aid and the provision of intelligence information to Kyiv” if any ceasefire is to become permanent.
The PM’s spokesman said: “Russia should agree to an unconditional ceasefire. Ukraine has done so without conditions.
“We all want to see an end to this fighting. The ball is now in Russia’s court.”
The spokesman also condemned Russia’s “barbaric” attacks on Ukraine overnight, which came after Putin’s call with Trump.
Meanwhile, Starmer told the Commons that he had reaffirmed the UK’s “unwavering support” for Kyiv in a call with Ukrainian president Volodymyr Zelensky on Tuesday.