In an extraordinary speech from the ceremonial room at the White House, Donald Trump claimed victory a short time ago, although millions of votes have yet to be counted in what is clearly a tight race.
"We did win this election", he said, "this is a fraud on the American public"
Earlier, Democrat candidate Joe Biden gave a short speech from his base in Delaware and told supporters he thought the Democrats were positioned to win but that they must be patient.
With many votes still to be counted, all eyes are on the key battleground states of Michigan, Pennsylvania and Wisconsin.
US television networks predict that the Democrats will hold their majority in the House of Representatives but the result in the Senate is hard to predict.
Outside the White House, a peaceful gathering of mostly anti-Trump protestors turned heated briefly when a gas canister was thrown but calm has been restored.
To take the presidency, a candidate must win 270 Electoral College votes.
It is possible to win a majority of the popular vote but not enough states to become president, as happened with Hillary Clinton in 2016.
At the moment, candidates are both neck and neck in the popular vote.
