Democrat Joe Biden has attacked Mr Trump’s refusal to concede defeat, calling attacks on the election and election officials “simply unconscionable” and attempts to overturn the result an “abuse of power”.
The comments come as Mr Biden won the state-by-state Electoral College vote that formally determines who is the next US president.
The victory has all but ended President Donald Trump‘s floundering campaign to overturn his loss of the US presidential election last month.
California – the most populous state – delivered its 55 electoral votes to Mr Biden on Monday afternoon, officially taking him over the 270 votes needed to secure the White House.
When all of the states finish voting, Mr Biden is expected to lead Mr Trump 306-232.
Addressing the nation from his long-time home of Wilmington, Delaware, Mr Biden said: “If anyone didn’t know it before, we know it now. What beats deep in the hearts of the American people is this: Democracy.
“The right to be heard. To have your vote counted. To choose the leaders of this nation. To govern ourselves.”
Mr Biden said politicians in the US “don’t take power – the people grant it to them”, adding: “Nothing, not even a pandemic – or an abuse of power – can extinguish that flame.”
He also renewed his campaign promise to be a president for all Americans, whether they voted for him or not, and said the country has hard work ahead on coronavirus and the economy.
Hours after Mr Biden was confirmed as the winner in the US presidential race, Russian leader Vladimir Putin offered his congratulations to the former vice president.
Mr Putin had been notably quiet in the weeks following the election, but in a statement, the Kremlin said on Tuesday: “Putin wished the president-elect every success and expressed confidence that Russia and the United States, which have a special responsibility for global security and stability, could, despite their differences, really help to solve the many problems and challenges facing the world.”
It comes as Mr Trump announced that attorney general William Barr would be stepping down from his role.
He is resigning amid lingering tension with the president over Mr Trump’s claims of election fraud and the investigation into Mr Biden’s son, Hunter.
“As per letter, Bill will be leaving just before Christmas to spend the holidays with his family,” Mr Trump tweeted.
We’ve seen a lot of end of the road moments for Mr Trump, but today is one of the biggest.
After multiple failed legal challenges to overturn the election, it was time for 538 electors to meet in their respective states to cast their votes for the president and vice president.
States have been certifying their results in what has been a kind of rubber-stamping exercise, albeit pivotal in cementing victory.
It usually passes without much fanfare or comment. It is typically a dry, procedural affair, but Mr Trump’s refusal to accept Mr Biden as the winner injected some jeopardy into the occasion.
In Michigan, the state capitol was closed to the public because of perceived “credible threats of violence”, an official said.
In Arizona, electors had to cast their votes in a secret location due to threats.
The president may have succeeded in sowing doubt about the electoral process among a proportion of his followers, but the electors in the key swing states he’s been trying so hard to win back, re-confirmed his defeat.
Mr Biden not only won the 2020 election, but decisively – getting back the all-important Rust Belt, but he also upset decades of Republican dominance in Arizona and Georgia.
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Stacey Abrams, an elector critical in driving the vote for Mr Biden in Georgia, reminded the country of the challenge ahead. America, she said, is still grappling with “who we intend to be as a nation”.
In previous years, so-called faithless electors, who stray from the popular vote, have been factor in the electoral college vote. It is rare, but this year, there has been hardly any talk of people switching from Mr Biden to Mr Trump in any meaningful way to change the outcome.
Mr Trump’s fate was arguably sealed a long time ago. But on Friday came a critical blow. The Supreme Court, filled with three Conservative justices he picked, rejected his eleventh hour bid to overturn the election based on a Texas lawsuit.
He tried to remove electors in some states ahead of today’s vote but the highest court in the land refused to support that effort.
The next big moment for the electoral process is 6 January, when Congress gathers to count the electoral votes. At that point the winner will be announced by Mike Pence, who presides over the Senate as vice president.
Mr Biden will take office at the inauguration on 20 January. It seems unlikely that we will see any big concession from Mr Trump between now and then. He is already dangling the prospect of announcing a 2024 bid, on the same day.