Biden also was expected to announce as soon as Monday top members of his economic team
President-elect Joe Biden chose more senior aides to lead his administration's efforts to defeat the coronavirus and rebuild the US economy, and his office confirmed on Sunday he would begin receiving classified briefings that are an essential step toward taking control of national security.
As the Democratic former vice president prepared for his move to the White House, Republican President Donald Trump pledged to maintain his legal fight to overturn the result of the November 3 vote even while indicating in comments to Fox News that he was growing resigned to leaving office on January 20.
On Monday, Biden will begin receiving the classified presidential daily briefing, after weeks of the Trump administration refusing to provide it. The PDB, as it is known, is the first step toward transfer of responsibility for the most sensitive intelligence to a new administration.
Biden also was expected to announce as soon as Monday top members of his economic team, a source familiar with the process said. They include several officials with whom Biden worked when serving as vice president to Barack Obama.
Neera Tanden, president of the progressive Center for American Progress think tank, will be named director of the Office of Management and Budget, and Cecilia Rouse, a labor economist at Princeton University, would be named as chair of the Council of Economic Advisers, the source said.
The picks were initially reported by the Wall Street Journal. The New York Times also reported on Sunday that Brian Deese, who helped lead Obama's efforts to bail out the automotive industry during the 2009 financial crisis, would head the National Economic Council.
Biden also tapped campaign staff and advisers to lead an all-woman communications team, naming campaign spokeswoman Kate Bedingfield as White House communications director and veteran Democratic spokeswoman Jen Psaki as press secretary.
Separately, the 78-year old Biden visited a doctor as a precautionary measure on Sunday after injuring his ankle when playing with one of his dogs.
Despite Trump's pledge to keep fighting, a few Republicans appeared to acknowledge that Biden had won.
"We're working with the Biden administration, the likely administration, on both the transition and the inauguration as if we're moving forward," Senator Roy Blunt, chairman of the congressional inaugural committee, told CNN, stopping short of acknowledging that Trump lost.
Trump on Sunday kept up his unsubstantiated allegations of widespread electoral fraud, both in his Fox News interview and on Twitter. His legal team has lost dozens of lawsuits by failing to convince judges of election irregularities in hotly contested states like Michigan, Georgia and Arizona.
Biden won with 306 Electoral College votes - only 270 are required - to Trump's 232. The former vice president also leads Trump by more than 6 million in the popular-vote tally.
Trump's team was dealt another blow with the completion on Sunday of recounts in Wisconsin's two largest counties that confirmed Biden won the battleground state by more than 20,000 votes.
Speaking to Fox News, the president was unclear about how he would proceed. "The problem is it's hard to get it to the Supreme Court," he said.
Trump's team has offered conflicting statements on its likely course following a defeat in a federal appeals court on Friday in a case challenging Biden's win in Pennsylvania.
The Supreme Court has always been unlikely to tip the election in Trump's favor, said Jessica Levinson, a professor at Loyola Law School in Los Angeles.
Trump's Pennsylvania challenge was a particularly poor vehicle for getting to the high court because it involves a procedural question about whether Trump's campaign should have been allowed to expand the case, Levinson said.
"There is nothing for the Supreme Court to decide," she said.
Trump said for the first time on Thursday that he would leave the White House if the Electoral College votes for Biden on December 14. On Sunday, he said he would continue to fight the results of the election even after he is due to leave office, saying: "My mind will not change in six months."
Aides say Trump has discussed starting a television channel or social media company to keep himself in the spotlight ahead of a potential 2024 White House bid.