Joe Biden has promised to be a “President for all Americans” after topping the 270 electoral college votes needed for victory over Donald Trump in the US presidential race.

The former vice-president was called as the winner of Pennsylvania on Saturday, meaning he has an insurmountable lead in the race for the White House.

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Mr Biden said on Twitter: “America, I’m honoured that you have chosen me to lead our great country.

“The work ahead of us will be hard, but I promise you this: I will be a President for all Americans — whether you voted for me or not.

“I will keep the faith that you have placed in me.”

In a statement, Mr Biden said: “I am honoured and humbled by the trust the American people have placed in me and in Vice President-elect Harris.

“In the face of unprecedented obstacles, a record number of Americans voted. Proving once again, that democracy beats deep in the heart of America.

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“With the campaign over, it’s time to put the anger and the harsh rhetoric behind us and come together as a nation.

“It’s time for America to unite. And to heal.

“We are the United States of America. And there’s nothing we can’t do, if we do it together.”

Mr Trump made a series of unsubstantiated allegations to claim he is being cheated out of re-election, while Mr Biden had called for calm as votes in key battleground states were counted well past November 3.

On Saturday morning, a top election official dismissed Mr Trump’s fresh claims of voter fraud.

But Federal Election Commission commissioner Ellen Weintraub said there has been no evidence of voter fraud.

Speaking on CNN after Mr Trump’s string of tweets – which were flagged by Twitter as containing information about the election that may be “misleading” – Democrat Ms Weintraub said: “State and local officials, and poll workers throughout the country, really stepped up.

“And there have been very few complaints about how this election has run.

“Very few substantiated complaints, let me put it that way. There is no evidence of any kind of voter fraud.