UK Prime Minister Boris Johnson is among politicians to have congratulated Joe Biden on his US election win.
He said he looked forward to “working closely” with the new president-elect.
Labour leader Sir Keir Starmer praised Mr Biden’s campaign of “decency, integrity, compassion and strength”.
Vote counting continues after Tuesday’s election, but the BBC projected on Saturday that Mr Biden has surpassed 270 electoral college votes – the threshold required to win.
Donald Trump’s campaign has indicated the incumbent president does not plan to concede.
Mr Johnson said in a statement on Twitter on Saturday: “The US is our important ally and I look forward to working closely together on our shared priorities, from climate change to trade and security.”
Mr Johnson also congratulated the president-elect’s running mate, Kamala Harris, on “her historic achievement”. She will be the country’s first female vice-president.
Sir Keir said on Twitter that Mr Biden’s campaign was based on “decency, integrity, compassion and strength”, which are “values that we in the United Kingdom share”.
Foreign Secretary Dominic Raab said Mr Trump had “fought hard” but that he was looking forward to working with the new administration.
“The UK-US friendship has always been a force for good in the world,” he added.
‘Special relationship’ may face downgrade
They won’t be seen as natural allies: Joe Biden, the seasoned Democrat, and Boris Johnson, the bombastic Brexiteer.
In looking at how their future relationship might work, it’s worth considering the past. Specifically that seminal year, 2016, when Donald Trump won the White House and the UK voted to leave the EU. Both Mr Biden and his boss at the time, Barack Obama, made no secret they preferred another outcome on Brexit.
The UK government’s recent manoeuvres in relation to Brexit have not gone down well with key Democrats and the Irish lobby, including the US president-elect. Mr Biden said he would not allow peace in Northern Ireland to become a “casualty of Brexit” if elected – stating that any future US-UK trade deal would be contingent upon respecting the Good Friday Agreement.
The “special relationship” could, feasibly, face a downgrade. However, the two men may yet find some common ground.
The leader of the Liberal Democrats, Sir Ed Davey, said the result was “a great victory for social justice, climate action and democracy”.
First Minister of Scotland Nicola Sturgeon also shared her congratulations, while SNP Westminster leader Ian Blackford said the win “gives great hope to progressives here in Scotland and around the world”.
First Minister of Wales Mark Drakeford tweeted that he was looking forward to working with Mr Biden “to build on the strong links between Wales and USA”.