Democrat Joe Biden has won the US presidential election defeating Donald Trump. 

His victory came after more than three days of uncertainty as election officials sorted through a surge of mail-in votes that delayed the processing of some ballots. Biden, 77, crossed 270 Electoral College votes with a win in Pennsylvania.

In a tweet he said he would work for "all Americans". 

Trump seized on delays in processing the vote in some states to allege unsubstantiated  claims of voter fraud and argue that his rival was trying to seize power. 

Trump said in a tweet an hour before the vote was called that he was in fact the winner. 

The Trump campaign has indicated their candidate does not plan to concede.

The result makes Trump the first one-term president since 1992.

Meanwhile, Biden will be the oldest president ever to serve. It was his third try for the top job. 

Kamala Harris also made history as the first Black woman to become vice president, an achievement that comes as the US faces a reckoning on racial justice. The California senator, who is also the first person of South Asian descent elected to the vice presidency, will become the highest-ranking woman ever to serve in government, four years after Trump defeated Hillary Clinton.