Washington - The decision frees up millions of dollars in financing to support the transition, allowing Biden to coordinate with govt officials.
President Donald Trump gave some ground on Monday to allow Joe Biden's transition to the presidency after the ranks grew of prominent Republicans calling for Trump to end efforts to overturn his election defeat.
Twenty days after Election Day, most members of Trump's party still refused on Monday to refer to Biden as president-elect, or question Trump's insistence - without evidence - that he only lost on November 3 because of fraud.
The ground shifted significantly, however, late on Monday. Trump gave the go-ahead for federal funds to start flowing to Biden so that he can carry out his transition duties before his Jan. 20 inauguration as the 46th US president.
Trump, however, did not formally concede the election to Biden. And leading Republicans in Congress, including Senate Majority Leader Mitch McConnell and House Minority Leader Kevin McCarthy, offered no immediate reaction as the way appeared to clear for Biden to be fully recognized as president-elect.
Intensifying pressure from some Republicans may have factored in Trump's move to allow funding for Biden's transition. But possibly as consequential, if not more, was Michigan's certification of Biden's victory in that state.
Trump's legal team has also suffered a string of judicial defeats in its bid to prevent states from certifying Biden as the presidential election winner, and legal experts say the remaining cases do not give Trump a viable path to overturning the election results.
Republican Senator Shelley Moore Capito, who represents West Virginia, which overwhelmingly backed Trump, issued a statement earlier on Monday saying there was no indication that any election irregularities were widespread enough to call Biden's victory into question.
Republican Senator Rob Portman - co-chairman of Trump's campaign in Ohio who rarely breaks with party leaders - said there was no evidence of widespread election fraud and called for the transition to begin.
"It is now time to expeditiously resolve any outstanding questions and move forward," Portman wrote in a Cincinnati Enquirer opinion column on Monday.
However, Portman did not refer to Biden as "president-elect" and referred to his becoming the next president as a "likely event." Capito also did not refer to Biden as president-elect.
Senator Lamar Alexander, who is retiring from his Tennessee Senate seat at the end of the year, called on Trump to "put the country first and have a prompt and orderly transition to help the new administration succeed."
In a statement issued after Michigan certified its election results in a blow to Trump's efforts to overturn the election, Alexander said, "When you are in public life, people remember the last thing you do."
Calls for Trump to accept defeat have been stronger outside Washington, even from some of his staunchest supporters, including former New Jersey Governor Chris Christie, who called Trump's behavior "a national embarrassment" in an interview on ABC.
And more than 100 former Republican national security officials published a letter on Monday asking that party leaders denounce Trump's refusal to concede, calling it a dangerous assault on democracy and national security.