Joe Biden will be officially declared US president-elect as all the American states’ Electoral College votes are cast on Tuesday.

Electors have gathered in 50 US states and the District of Columbia to formally vote for Mr Biden as the next US president, by which point Donald Trump will have officially failed to overturn his November 3 election loss.

It comes less than a week after the Supreme Court rejected a Republican bid to throw out up to 2.5 million mail-in ballots in Pennsylvania.

Mr Trump has sought to upend the Electoral College vote that would confirm Mr Biden’s presidential win and continues to claim a fraudulent election.

“Why did the Swing States stop counting in the middle of the night?” @MariaBartiromo Because they waited to find out how many ballots they had to produce in order to steal the Rigged Election. They were so far behind that they needed time, & a fake “water main break”, to recover!

— Donald J. Trump (@realDonaldTrump) December 14, 2020

Early on Tuesday (Australian time), Vermont’s three representatives to the Electoral College cast the state’s presidential ballots for Mr Biden and vice president-elect Kamala Harris.

In Tennessee, 11 representatives cast their votes for Mr Trump and Vice President Mike Pence.

Four Electoral College votes from New Hampshire went to Mr Biden and 11 from Indiana went to Trump.

Electors in other states also have begun voting.

Most states have laws binding their electors to the winner of the popular vote in their state.

The results will be sent to Washington DC and tallied in a January 6 joint session of Congress over which Mr Pence will preside.

The electors’ votes have drawn more attention than usual in 2020 because Mr Trump has refused to concede the election and continues to make allegations of fraud.

Election officials across the US have repeatedly said there were no instances of widespread fraud.

-with AAP