Boris Johnson said the UK and US will work “hand in hand” after Joe Biden takes office.
The UK Government believes Mr Biden’s inauguration as US president on Wednesday marks the start of a new political era following the turbulence of Donald Trump’s administration.
Mr Biden will be sworn in as the 46th president of the United States in Washington amid unprecedented security after a pro-Trump mob stormed the Capitol earlier this month.
The UK’s ambassador to the US, Dame Karen Pierce, said there was “a lot of optimism” in Washington ahead of the inauguration ceremony, which has been scaled back as a result of coronavirus measures.
She suggested that Mr Biden would be a more predictable partner for the UK – but defended Mr Trump’s unorthodox approach to international affairs.
“There were certain things about the way Donald Trump, President Trump, did business that made it harder for certain quarters, the Russians would be one, to second guess him, and that sometimes has a utility,” she told BBC Radio 4’s Today.
“But I think the whole of the diplomatic corps is very pleased to see American democracy come out on top.”
The Prime Minister is viewed with suspicion by some influential Democrats who regard him as “Trump clone” – an image that he is anxious to shake off.
In his statement, Mr Johnson pointed to the continuing common interests the UK and the US share on defence, security and “defending democracy”.
At the same time, he highlighted Britain’s upcoming role in chairing the G7 summit in Cornwall and the Cop26 climate change conference in Glasgow – both priorities for the new administration, as the world recovers from the coronavirus pandemic.
Mr Johnson said: “In our fight against Covid and across climate change, defence, security and in promoting and defending democracy, our goals are the same and our nations will work hand in hand to achieve them.
“I look forward to welcoming him to Carbis Bay for the G7 and Glasgow for Cop as we join forces to protect our planet.
“Only through international co-operation can we truly overcome the shared challenges which we face.”
Home Secretary Priti Patel said the change in the White House would have an impact around the world.
“There is a change in presidency but, as ever, when administrations change, the world changes, the direction of travel – from politicians in particular, political leaders – always reflect some of the challenges and changes that we see going on domestically and internationally,” she told Sky News.
“A new political era is now starting in America and there is a lot to do globally, there really is, as well as in the US – certainly uniting the United States at the end of the Trump administration and as Joe Biden takes over.”