US Attorney General William Barr says his justice department has found no proof to back President Donald Trump’s claims of fraud in the 2020 election.
“To date, we have not seen fraud on a scale that could have effected a different outcome in the election,” he said.
His comments are seen as a big blow to Mr Trump, who has not accepted defeat.
He and his campaign have filed lawsuits in states that he lost, as they begin certifying Joe Biden as the winner.
President-elect Biden defeated the incumbent Mr Trump by a margin of 306 to 232 votes in the US electoral college, which chooses the US president. And in the popular vote, Mr Biden won at least 6.2 million more votes than Mr Trump.