Three days after election day on Nov 3, Democratic presidential candidate Joe Biden moved into the lead in the crucial battleground states of Pennsylvania and Georgia yesterday, putting him on track to win the presidency and potentially cutting off President Donald Trump's remaining paths to victory.

Mr Trump was trailing in all the outstanding swing states that have not been called except for North Carolina, which Mr Biden does not need to reach the 270 electoral votes required to win the election.

The Trump campaign did not take the news lying down, releasing a statement shortly afterwards that rejected the numbers and repeated the claim that Mr Trump would be re-elected.

"This election is not over," said campaign lawyer Matt Morgan. "The false projection of Joe Biden as the winner is based on results in four states that are far from final."

Pennsylvania was always the prize for the Biden-Kamala Harris ticket, and its 20 electoral votes would put Mr Biden over the top with the states he now holds.

He pulled ahead in the north-eastern state that Mr Trump captured in 2016 just before 9am Eastern Time (10pm Singapore time), when more results were released that put him at 5,600 votes, or 0.1 point, ahead of the President.

Mr Trump's lead had steadily eroded over the last few days as votes from heavily Democratic Philadelphia and its surrounding areas were counted.

By press time past midnight, Mr Biden's lead had widened to 8,867, with more votes still to be counted.

Mr Biden was also 1,585 votes ahead of Mr Trump in Georgia - which has 16 electoral votes - where 99 per cent of the votes have been counted.

Aside from Georgia and Pennsylvania, votes were still being counted in Nevada, where he widened his lead overnight, and Arizona. In Arizona, Mr Trump narrowed Mr Biden's lead to about 43,000 votes, or 1.4 points, but he will need about 60 per cent of the remaining votes to overtake Mr Biden.

With votes continuing to be tallied amid these razor-thin margins, the former vice-president urged patience on Thursday and rejected Mr Trump's unsubstantiated claims of voter fraud made in an address to the nation from the White House.

"The people will not be silenced, be bullied or surrender. Every vote must be counted," Mr Biden wrote on Twitter. "No one is going to take our democracy away from us. Not now, not ever. America has come too far, fought too many battles and endured too much to let that happen."

Asked for his response to reports that Mr Trump had no plans to concede the election, Biden campaign spokesman Andrew Bates said: "As we said on July 19, the American people will decide this election. And the United States government is perfectly capable of escorting trespassers out of the White House."

As counting continued in the handful of states still remaining, Americans rallied in support of both the President and Mr Biden, either demanding a stop to the count outside voting centres or that every vote be tallied.

Mr Biden was also solidly ahead in the popular vote, with yesterday morning's count showing that 73.5 million Americans, or 50.5 per cent, voted for him, while 69.6 million, or 47.9 per cent, voted for Mr Trump.

The US Secret Service, which is in charge of protecting America's top leaders, sent more agents to Wilmington, Delaware, where Mr Biden lives, in anticipation of his potential win, The Washington Post and CNN reported.

On Wednesday, the Federal Aviation Administration posted a one-mile-radius no-fly zone over Mr Biden's home.