The top Republican in the U.S. Congress on Monday said President Donald Trump was well within his rights to look into charges of "irregularities" in last week's election, which has been called for Democrat Joe Biden, but did not offer any evidence of fraud.

Trump, a Republican, has yet to acknowledge defeat two days after Biden secured enough votes in the state-by-state Electoral College to win. 

Senate Majority Leader Mitch McConnell said he backed Trump's launch of a legal fight into claims of voter fraud.

"President Trump is 100 percent within his rights to look into allegations of irregularities and weigh his legal options," McConnell said.

McConnell spoke after four Senate Republicans, including a prominent Trump critic, acknowledged Biden's victory. Before addressing the Senate, he met privately with Attorney General William Barr.

(With input from Reuters)