Keir Starmer and Joe Biden have pledged to do “whatever it takes” to help Ukraine defeat Vladimir Putin.
The pair met for talks in the White House on Wednesday evening for the first time since Labour’s landslide election victory last week.
In a statement released this morning, a No10 spokesperson said: “They reflected on the importance of the Nato alliance and the special relationship in the context of current geopolitical challenges, including the ongoing war in Ukraine.
“They agreed we must continue to do whatever it takes to support Ukraine and ensure aggressors like Putin do not win.”
Starmer also held talks with Volodymyr Zelenskyy in Washington, after which the Ukrainian president said his country now had permission to use British Storm Shadow missiles to attack targets in Russia.
That would mark a major escalation in the UK’s involvement in the conflict, which began nearly two-and-a-half years ago.
Writing on X, Zelenskyy said: “Had the first meeting with the new Prime Minister of Great Britain, Keir Starmer. Thank you for all the military and financial packages for our country.
“In the morning, I read about the permission to use Storm Shadow missiles against military facilities on the territory of the Russian Federation.
“And today we had the opportunity to discuss the practical implementation of this decision. Thank you for your constant support of Ukraine and our people!”
The prime minister has also confirmed that the UK will continue to spend £3 billion a year supporting Kyiv for as long as the war continues.
Asked on Sky News this morning about the risk of Russian retaliation against Britain, security minister Dan Jarvis said: “In concert with our Nato allies, we work together to make sure that President Zelenskyy and Ukraine have got the material support that they need to defend themselves against Russia.
“It is an illegal invasion, the consequences of which are massive for the whole of the world and we stand shoulder to shoulder with our allies to do what we can to support our allies in Ukraine.”