Biden, the Democratic former vice president, has spent days huddled with advisers as he weighs whom to appoint to his cabinet, fields congratulatory calls from world leaders and maps out the policies he will pursue after being sworn in on January 20.

He is expected to continue meeting with advisers in private on Sunday.

Meanwhile, Republican Trump has refused to concede and instead pressed unsubstantiated allegations of fraud, stalling the government's normal process of preparing for a new presidential administration.

His campaign has filed lawsuits seeking to overturn the results in multiple states, though without success, and legal experts say the litigation stands little chance of altering the outcome of the November 3 election.

Election officials of both parties have said there is no evidence of major irregularities.

The "Million MAGA March," referring to Trump's campaign slogan of "Make America Great Again," drew a crowd of flag-waving supporters to downtown Washington on Saturday.

"Hundreds of thousands of people showing their support in D.C. They will not stand for a Rigged and Corrupt Election!" the president wrote on Twitter, though most crowd estimates were well short of Trump's figure.

Trump's motorcade passed through the crowd on its way to his golf course in Virginia, producing cheers from demonstrators as the president waved from the back seat.

Dozens of Proud Boys, a far-right group, marched in the streets, some wearing helmets and ballistic vests, while members of the loose far-left movement known as antifa staged their own counter-demonstrations.

The city's police force arrested at least 10 people, including several who were charged with assault.

Biden has won 306 votes in the state-by-state Electoral College system that determines the presidential winner, according to Edison Research, far more than the 270 needed to secure a majority.

Trump earned the same number of electoral votes in 2016 over Democratic candidate Hillary Clinton, a victory he has called a "landslide" despite the fact that she won the national popular vote.

Biden has also won the popular vote: with a few states still counting ballots, he leads Trump by more than 5.5 million votes, or 3.6 per cent.

With his chances of reversing the outcome virtually extinguished, Trump has discussed with advisers potential media ventures that would keep him in the spotlight ahead of a possible 2024 White House bid, aides said.

But his public claims of a "rigged" election have prevented Biden and his team from gaining access to government office space and funding normally afforded to an incoming administration to ensure a smooth transition.

The federal agency in charge of providing those resources, the General Services Administration, has yet to recognise Biden's victory.

States are in the process of certifying their election results. The Electoral College meets to vote for the new president on December 14.

The raging pandemic will likely be Biden's top priority. The US set a new daily record of new cases on Friday for the fourth straight day.

More than 244,000 people in the country have died of the coronavirus since the pandemic began.

Australian Associated Press