In their first face-to-face talks, held in the Oval Office, the US President urged the new Prime Minister to return to being America’s point man for the European Union.
His comments come after Sir Keir said he wanted to use the Nato summit to start softening Brexit within days.
President Biden said: “I kind of see you guys as the knot tying the transatlantic alliance together, the closer you are with Europe.
“We know where you are, you know where we are.”
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The men met after England booked their place in the World Cup final with a sensational two-one victory over the Netherlands.
Asked if he had watched the football, the president said it was “good news indeed”.
“It’s all because of the Prime Minister,” he added.
Pressure on Mr Biden to quit over his health mounted as actor George Clooney said he cannot win “the fight against time”.
The influential Democratic fundraiser said wrote in the New York Times that it was "devastating to say it", but the Joe Biden he met at a fundraising event three weeks ago was not the Biden of 2010.
"He wasn’t even the Joe Biden of 2020," added the actor. "He was the same man we all witnessed at the debate," Clooney said.