Trump’s slender lead in the battleground state of Georgia continued to narrow as the state seeks to wrap up its count, while the count in other states is also favouring Biden.

Addressing the nation on Wednesday afternoon US time, Biden declared he had won Wisconsin by 20,000 votes, and was leading in Michigan by a margin bigger than US President Donald Trump won the state with in 2016.

“After a long night of counting, it’s clear that we’re winning enough states to reach 270 electoral votes needed to win the presidency,” he said.

“I’m not here to declare that we’ve won. But I am here to report, when the counting is finished, we believe we will be the winners.”

Biden this morning carried Michigan and its 16 electoral votes, further dismantling Donald Trump’s Rust Belt wall of support that helped deliver him the presidency four years ago.

The flip from red back to blue was a huge blow to Trump, whose victories in Michigan, Wisconsin and Pennsylvania in 2016 sent him to the White House. Biden also carried Wisconsin, though Pennsylvania hasn’t been called yet.

Biden’s victory in Michigan pushes him to 264 Electoral College votes, six short of the 270 needed to win the White House. Trump is at 214 electoral votes.

Nevada, which has six electoral votes, is among the states Democrat Hillary Clinton won in 2016 that hasn’t yet been called.

Saying the election had been “a long and difficult campaign”, Mr Biden stressed the need for Americans to “come together” and “heal” once a result had been finalised.

“We’ve had hard campaigns before. We’ve faced hard times before. So, once this election is finalised and behind us, it will be time for us to do what we’ve always done as Americans … respect and care for one another,” Mr Biden said.

“To unite. To heal. To come together as a nation.

“I know this won’t be easy. I’m not naive. Neither of us are. How deep and hard the opposing views are in our country … but to make progress, we have to stop treating our opponents as enemies.”

Trump’s campaign says it will seek a recount of votes in Wisconsin, hours after CNN and the Associated Press projected Democrat Joe Biden had won the key battleground state’s 10 electoral college votes.

“There have been reports of irregularities in several Wisconsin counties which raise serious doubts about the validity of the results,” Trump campaign manager Bill Stepien said in a statement, without providing details of any reports.

“The President is well within the threshold to request a recount and we will immediately do so.”

Election experts say fraud is very rare in US voting.

Edison Research said the margin between Trump and Biden in Wisconsin was less than one percentage point, allowing a candidate to seek a recount.

It said Biden had a slight lead in the state, with 99 per cent of the expected votes tallied so far. The former vice president had 49.4 per cent of the vote, while Trump had 48.8 per cent.

The CNN and AP projections would raise Biden’s tally of electoral votes, but several states have not been called for either candidate.

The CNN tally puts Biden at 234 of the 270 votes needed to win the White House, versus 213 for Trump. AP’s tally stands at 238 to 213.

Biden also led in another critical midwestern battleground state – Michigan – as he and Trump raced to get to the 270 electoral votes in the state-by-state electoral college needed to win the White House.

Trump won Wisconsin and Michigan in his 2016 election victory.

Wisconsin officials finished their tally at about midday after an all-night effort, showing Biden with a lead of just over 20,000 votes, or 0.6 per cent, according to Edison Research.

A Biden victory in Wisconsin would significantly narrow Trump’s path to a second four-year term, though the outcome remained in doubt with Michigan and other closely contested states including Pennsylvania, Arizona, Nevada, Georgia and North Carolina still counting votes.

Trump led in the southern states of Georgia and North Carolina as well as in Pennsylvania, where more than 1 million ballots were yet to be processed.

But if Trump loses Wisconsin, he would have to win all three as well as either Arizona or Nevada, where Biden was leading in the latest vote counts.

At the moment, not including Wisconsin, Biden leads Trump 227 to 213 in electoral college votes, which are largely based on a state’s population.

In duelling conference calls with reporters earlier on Wednesday, officials from each campaign insisted their candidate would prevail.

“If we count all legal ballots, we win,” Trump campaign manager Bill Stepien said, potentially setting the stage for post-election litigation over the counting of mail-in ballots.

Biden campaign manager Jennifer O’Malley Dillon told reporters the former vice president was on track to win the election while senior legal adviser Bob Bauer said there were no grounds for Trump to invalidate lawfully cast ballots.

“We’re going to defend this vote, the vote by which Joe Biden has been elected to the presidency,” said Bauer, adding that the campaign’s legal team was prepared for any challenge.

Biden was expected to deliver an address later on Wednesday.

Meagan Wolfe, Wisconsin’s elections chief, said on Wednesday the state’s electoral officials were re-checking results after working through the night to count valid ballots.

“Wisconsin’s counting and reporting of unofficial results has gone according to law,” she said in a statement.

“Today, the Wisconsin Elections Commission staff will be standing ready to assist clerks as they start the process of triple-checking the results.”

That process would include randomly selecting five per cent of reporting units for voting equipment audits required before results can be certified on December 1, she said.

No comment was immediately available from Wisconsin officials about whether the Trump campaign had submitted a formal recount request.

-AAP