Democratic challenger Joe Biden holds a slim lead over President Donald Trump.

But with millions of votes yet to be counted in key states including Pennsylvania and Michigan, it’s still anyone’s race to the White House.

By early Thursday morning (Australian time), the Associated Press was reporting that the Democrats had flipped Wisconsin, the state that went to Mr Trump in 2016 (the first Republican presidential candidate to win there in more than 30 years).

Mr Biden is cautiously “optimistic” and Democrats said they were hopeful of having a result by Thursday afternoon (Australian time).

The fact that a result is still hours away – at the earliest – and that it looks like his rival has won another key state, hasn’t stopped Mr Trump falsely claiming victory.

Predictably, his team has also demanded a recount in Wisconsin.

Australian Foreign Minister Marise Payne said she remains confident of a clear result in the election.

”I’m confident that the US systems and processes that have stood the test of time will deliver an outcome and it is important that we wait for that,” Senator Payne told the ABC on Thursday.

“It’s important that we respect that process, that every vote is counted, and I’m sure that they will be.”

Earlier, in a move no doubt designed to fuel theories of vote-rigging should the Republicans lose, the president made a speech in which he alleged ‘‘a major fraud on our nation’’ had been committed in the US.

Americans rallied outside the White House to demand all votes are counted. Photo: AAP

“We want the law to be used in a proper manner, so we’ll be going to the US Supreme Court. We want all voting to stop,” the president told the nation in the late-night address packed with false information. 

“We don’t want them to find any ballots at 4 o’clock in the morning and add them to the list. It’s a very sad moment.”

Not content with the disruption caused by his dramatic announcement, Mr Trump has doubled down by taking to social media to claim that he was winning before votes began “magically disappearing”. 

Facebook and Twitter quickly hid some of the posts behind a notice warning users that “some or all of the content” in the message “is disputed and might be misleading about an election or other civic process”.

In one, Mr Trump claimed to have been leading Mr Biden in many Democratic-run states until “one by one”, the votes “started to magically disappear as surprise ballot dumps were counted”.

In a nation where shopkeepers have been boarding up windows, and the National Guard is on standby for violence, the president’s behaviour has been widely viewed as dangerous and irresponsible.

Mr Trump’s former national security advisor John Bolton called the comments “some of the most irresponsible” a president had ever made.

“He has cast doubt on the integrity of the entire electoral process purely for his own personal advantage,” Mr Bolton said.

“It’s a disgrace.”

“This shows, I think, why he’s not fit to be president of the United States.”

Tweet from @realDonaldTrump

Mr Trump has repeatedly and without evidence suggested an increase in mail-in voting will lead to an increase in fraud, although election experts say that fraud is rare.

In another tweet, Mr Trump claimed his opponents “are trying to STEAL the Election” and suggested that votes were being cast after polls had closed. That post was also censored.

Facebook said it had begun notifying American users that votes were still being counted and a winner had not been projected after Mr Trump “began making premature claims of victory”.

Tweet from @fbnewsroom

In a speech from the White House at 2am (local time), Mr Trump had falsely claimed victory over Mr Biden despite the fact millions of votes were yet to be counted.

“We were getting ready to win this election. Frankly, we did win this election,” Mr Trump said.

His comments came shortly after Mr Biden said he was confident of winning the contest once all votes had been counted.

Mr Trump said he will go to the US Supreme Court to try to stop “all voting”.

“This is a major fraud on our nation. We want the law to be used in a proper manner.”

Again, he provided no evidence to back up his claim of fraud.

“We don’t want them to find any ballots at 4 o’clock in the morning and add them to the list,” Mr Trump said.

Tweet from @TeamTrump

Earlier in the night, Mr Biden had told his supporters to keep the faith and said that he was on a path to victory.

“We feel good about where we are,” Mr Biden said in his home state of Delaware.

“We believe we’re on track to win this election.”

“It’s not my place or Donald Trump’s place to declare who won the election.

“That’s the decision of the American people.”

Mr Trump’s most likely road to victory goes through Pennsylvania, a state he carried in 2016 and is currently leading in. 

If he wins there, he will have to win three of the other battleground states to secure 270 electoral votes.

If he doesn’t win Pennsylvania, he’ll have to sweep the remaining five.

Mr Biden’s most likely road to victory goes through Nevada and Wisconsin, states where he is currently leading in.

If Mr Biden wins those states, victories in Georgia, Michigan or Pennsylvania would give him enough to win.

-with AAP