US President Donald Trump on Wednesday falsely claimed that he had won the US election with millions of votes still uncounted and said he would go the Supreme Court to dispute the counting of votes.

“Frankly, we did win this election,” Trump said after claiming he was winning several battleground states where votes were still being tallied.

Trump's comments came after Democratic rival, Joe Biden, said he was confident of winning a contest that will not be resolved until a handful of states complete vote-counting over the next hours or days.

The Republican, who according to initial results is in a neck-and-neck race with Biden, said he would go to court and wanted "all voting to stop”.

"We'll be going to the US Supreme Court, we want all voting to stop. In fact, there is no more voting just counting," he said.

He appeared to mean stopping the counting of mail-in ballots which can be legally accepted by state election boards after Tuesday's election, provided they were sent in time.

Biden’s campaign said it would fight any efforts by Trump’s campaign to go to the US Supreme Court to prevent ballots from being tabulated.

In a statement, Biden campaign manager Jen O’Malley Dillon called Trump’s statement “outrageous, unprecedented and incorrect”.

O’Malley Dillon said the Biden campaign has “legal teams standing by ready to deploy to resist that effort”, adding "they will prevail."

There was also immediate backlash from Trump's own Republican backers.

"It's a bad strategic decision. It's a bad political decision," Chris Christie, a Trump advisor said of the middle-of-the-night speech.

Election laws in all US states require all votes to be counted. More votes still stood to be counted this year than in the past as people voted early by mail and in person in the face of the coronavirus pandemic.

Trump won the battlegrounds of Florida, Ohio and Texas, dashing Biden's hopes for a decisive early victory, but Biden said he was on track to winning the White House by taking three key Rust Belt states.

Biden, 77, was eyeing the so-called “blue wall” states of Michigan, Wisconsin and Pennsylvania that sent Trump, 74, to the White House in 2016 for possible breakthroughs once those states finish counting votes in hours or days to come.

Trump has repeatedly and without evidence suggested that an increase in mail-in voting will lead to an increase in fraud, although election experts say that fraud is rare and mail-in ballots are a long-standing feature of American elections.