Britain’s Foreign Secretary Dominic Rabb said the US election was "clearly a much closer race than we expected” while leading politicians across Europe called for patience as they anxiously awaited the result.
With a favourable post-Brexit trade deal in train with President Donald Trump, the UK's Conservative-led government would be keen to see him win.
Mr Raab tweeted that he had “full confidence in the checks and balances of the US system to produce a result”.
But he said there would be "slightly different contours of the opportunities and the risks" for the relationship with the US, depending on who won the race to the White House.
In an earlier tweet, Mr Raab said he was positive about the relationship between Britain in the US.
“We are confident it will go from strength to strength, whichever candidate wins the election," he said.
Prime Minister Boris Johnson’s government will have to work hard if Joe Biden becomes president because the Democrat is not keen on Brexit and would write off any trade deal if the political process in Northern Ireland were threatened.
Mr Johnson avoided commenting on the US election on Wednesday when he was asked about Mr Trump’s early claim to victory and his call to stop counting votes.
“We don’t comment as a UK government on the democratic processes of our friends and allies,” he told MPs.
Shadow foreign secretary Lisa Nandy said there was “no doubt in my mind that Britain's interest lies with a Joe Biden victory”.
Ms Nandy said a Biden administration would help to bring the world together to tackle the pandemic.
Mr Biden would want to rejoin the Paris Agreement on climate change and rid the world of nuclear weapons, "particularly in relation to Iran", she said.
In France, where President Emmanuel Macron’s relationship with Mr Trump has cooled considerably, the government told the public to await the result.
“We take note that the counting procedure is still ongoing," a government spokesman said. "France will obviously work with the American president who is elected from this."
The European Commission indirectly admonished Slovenian Prime Minister Janez Jansa, who appeared to prematurely congratulate Mr Trump on his re-election.
“We are awaiting for the authorities in charge of the vote count to announce the results,” a commission spokesman said.
“We will abide by whatever announcement is forthcoming officially by the relevant US authorities and we think that everybody should do likewise.”
German Finance Minister Olaf Scholz said all votes should be counted and the result should come "out of democratic elections in democratic procedures”.
“The US will be an important partner for us regardless of how the election goes," Mr Scholz said.
Guy Verhofstadt, former Belgium prime minister and senior member of the European Parliament, tweeted that a divided America showed how important a united EU was.
“Looking at the chaos across the Atlantic, I'm more certain than ever that Europeans are stronger together in an uncertain world,” Mr Verhofstadt said.
“Whatever the outcome, the EU needs to take its destiny into its own hands.”
Manfred Weber, leader of the European People’s Party, the largest political group in the European Parliament, said the “deep polarisation” of the US was a warning for Europe.
Mr Weber tweeted that democracy was in danger if people “lose the ability to compromise”.