A group of US senators say they will refuse to certify Joe Biden’s election victory unless a commission is set up to investigate alleged voter fraud.
The 11 senators and senators-elect, led by Ted Cruz, want a 10-day delay to audit the unsubstantiated allegations.
The move is not expected to succeed as most senators are expected to endorse Mr Biden in the 6 January vote.
President Donald Trump has refused to concede, repeatedly alleging fraud without providing any evidence.
His legal efforts to overturn results have been overwhelmingly rejected by the courts. He has only one minor win, concerning a small number of postal ballots in Pennsylvania, one of the states Mr Biden won in last year’s race.
Vice-President Mike Pence has stopped short of echoing Mr Trump’s allegations of election fraud. But on Saturday, his chief of staff Marc Short said Mr Pence “welcomes” this latest effort by lawmakers to “raise objections” on 6 January.
Congress is due on that day to certify last month’s verdict by the US Electoral College – a body that awards points for each state won by presidential candidates in November’s election.
The college concluded that Mr Biden won the race by 306-232, but this must be affirmed by Congress in what is normally a straightforward procedure.
At the end of the process, Vice-President Pence – in his capacity as president of the Senate – will be left to declare Mr Biden the winner.
Mr Biden and his vice-president, Kamala Harris, will then be sworn into office on 20 January.