Joe Biden has urged Britain to “get closer to Europe” in his first face-to-face talks with Keir Starmer.
The US president described the UK as the “transatlantic knot” linking the two continents as he met the new prime minister at the White House.
Sir Keir has vowed to renegotiate the Brexit deal, though he is concerned he could make concessions such as paying into Brussels’ budgets, although he has insisted Britain will not rejoin the customs union or single market.
Biden has made much of his Irish roots and, unlike his rival Donald Trump, has been accused of siding with the EU during the divorce disputes.
The meeting came as Sir Keir made his debut on the world stage by attending a Nato summit in Washington.
The prime minister said the visit was an opportunity to “renew” the military alliance and the “special relationship”.
The President said: “I see you as the glue that binds the transatlantic alliance together, the closer you are to Europe. We know where you are, you know where we are.”
Joe Biden described the UK as the “transatlantic knot” linking the two continents as he met the new prime minister at the White House
The meeting came as Sir Keir made his debut on the world stage by attending a Nato summit in Washington.
The two leaders were in the famous Oval Office of the White House last night.
Sir Keir told the president: “This special relationship is very important. It was forged in difficult circumstances, it endured for a long time and it is now stronger than ever.
“I am very pleased to be able to come to the Government so early to renew my commitment to NATO, to renew my commitment to the special relationship and to discuss these issues with you.”
Boris Johnson has been among those warning that Labour will water down agreed terms with the EU.
A UK government spokesman said Biden and Sir Keir “agreed that we must continue to do whatever is necessary to support Ukraine and ensure that aggressors like Putin do not win.”
The spokesman added: “The President welcomed the Prime Minister’s recent comments on building closer relations with our European counterparts, as well as the UK’s commitment to Aukus.”
The meeting came as Sir Keir prepared to urge Nato allies to support Ukraine “for as long as it takes” and confirmed that the UK’s £3bn-a-year military aid to kyiv will continue.
The prime minister, who met Ukrainian President Volodymyr Zelensky on the sidelines of a NATO summit in Washington yesterday, will later tell alliance members they must send a “clear message” to Russian leader Vladimir Putin.
UK military support to Ukraine will continue until at least 2030/31 and for as long as necessary.
In a special session on Ukraine at the Nato summit, Sir Keir will warn that the Euro-Atlantic region’s first line of defence is Ukraine’s trenches.
He will say: “NATO was founded by the generation that defeated fascism. They understood not only the value of our strength, but the strength of our values.
“Those values are under attack once again. Putin needs to hear a clear message that resonates from this summit: a message of unity and determination, that we will stand with Ukraine with whatever it takes, for as long as it takes, to defend our shared values and our shared security.”
The Washington summit consolidated Ukraine’s “irreversible” progress towards NATO membership, with a joint statement by the allies.
NATO leaders pose for a family photo at the start of the summit yesterday
But because of NATO’s Article V, which pledges mutual defense, the allies will not allow Ukraine to join while it is still at war, as that would trigger an immediate conflict with Russia.
NATO allies are stepping up their engagements over Ukraine as they await the results of the US presidential election in November, where Donald Trump has threatened to reduce American support.
Concerns about Biden’s plan to run for re-election were evident during his Oval Office meeting with Sir Keir.
The president did not directly respond to questions about George Clooney’s criticism after the actor and prominent Democratic supporter suggested he should drop out of the race.