WASHINGTON, Dec. 1 (Xinhua) -- U.S. Attorney General William Barr said on Tuesday that the Department of Justice (DOJ) has not seen evidence of widespread voter fraud that would change the outcome of the 2020 presidential election.

"To date, we have not seen fraud on a scale that could have affected a different outcome in the election," Barr told The Associated Press in an interview.

The attorney general also said the DOJ and the Federal Bureau of Investigation (FBI) have been working to follow up specific complaints and information they've received.

Sitting President Donald Trump's lawyers said in a statement that they believe Barr's "opinion appears to be without any knowledge or investigation of the substantial irregularities and evidence of systemic fraud."

U.S. states are moving to certify former Vice President Joe Biden's victory over Trump in the White House race, while the Republican had greenlighted his administration to begin the transition to the Democrat but refused to concede.