President-elect Joe Biden will announce the first of his Cabinet picks on Tuesday, aides said, including possibly for secretary of state, as he lays the foundation for his administration despite President Donald Trump's refusal to concede.

Longtime aide and veteran diplomat Antony Blinken was the most likely candidate to head the State Department, one Biden source said on Sunday. Bloomberg News reported earlier that Blinken would be the choice. Blinken could not be reached for comment.

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Biden said last week he had settled on a Treasury secretary. Former Fed Chair Janet Yellen is believed to be the top candidate in Democratic and monetary policy circles. A spokesman for Biden's transition declined to comment.

Ron Klain, Biden's choice as White House chief of staff, told ABC'S "This Week" that the first Biden Cabinet picks would come on Tuesday.

Klain again urged that the Trump administration - specifically a federal agency called the General Services Administration (GSA) - formally recognize Biden's victory in order to unlock resources for the transition process. "I hope that the administrator of the GSA will do her job," Klain added, referring to GSA chief Emily Murphy. Biden is due to take office on Jan. 20.

"A record number of Americans rejected the Trump presidency, and since then Donald Trump's been rejecting democracy," Klain told "This Week."

Since Biden, a Democrat, was declared the winner of the Nov. 3 election two weeks ago, the Republican president has launched a barrage of lawsuits and mounted a pressure campaign to try to prevent state officials from certifying their vote totals, suffering another emphatic legal setback on Saturday in Pennsylvania.

Biden received 6 million more votes nationwide than Trump and prevailed 306-232 in the state-by-state Electoral College system that determines the election's victor.

SCALED-DOWN INAUGURATION PLANS

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Klain said there would be "scaled-down versions of the existing traditions" for Biden's inauguration. Inauguration ceremonies and related events typically draw huge crowds to Washington. COVID-19 cases and deaths are surging in many parts of the country amid a pandemic that has killed more than 256,000 people in the United States.

"We know people want to celebrate. There is something here to celebrate," Klain said. "We just want to try to find a way to do it as safely as possible." Critics of Trump, including Democrats and some Republicans, have accused him of trying to undermine faith in the American electoral system and delegitimize Biden's victory by promoting false claims of widespread voter fraud.

"Fight hard Republicans," Trump wrote on Twitter on Sunday morning as he pressed his unsubstantiated narrative of voter fraud before playing golf in Virginia for a second day in a row.

Attempts to thwart certification of vote tallies have failed thus far in courts in Pennsylvania, Georgia, Michigan and Arizona. U.S. District Judge Matthew Brann, in dismissing the Pennsylvania lawsuit on Saturday, compared the Trump team's arguments claiming voter fraud to a "Frankenstein's Monster" that was "haphazardly stitched together" using meritless legal arguments and speculative accusations.

Trump's campaign issued a statement on Sunday distancing itself from Sidney Powell, a lawyer who made baseless allegations of a vast vote-rigging conspiracy at a campaign news conference on Thursday.

"Sidney Powell is practicing law on her own," Trump campaign lawyers Rudy Giuliani and Jenna Ellis said in the statement. "She is not a member of the Trump Legal Team. She is also not a lawyer for the President in his personal capacity."Both Giuliani and Ellis attended the Thursday news conference alongside Powell. Powell did not immediately respond to a request for comment.

Trump's campaign also said it was appealing Brann's decision to the 3rd U.S. Circuit Court of Appeals. Pennsylvania is expected to send its county results to its top election official for certification on Monday.

Trump's campaign has filed a petition for another recount in Georgia. A previous laborious hand recount reaffirmed Biden's victory by a margin of more than 12,000 votes in the Southern state, a longtime Republican bastion in presidential elections.

'NATIONAL EMBARRASSMENT'

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Some of Trump's fellow Republicans are now breaking ranks, although many, including the most senior ones in Congress, have not. Former New Jersey Governor Chris Christie, who has served as a Trump adviser, called the president's legal team a "national embarrassment."

"They allege fraud outside the courtroom, but when they go inside the courtroom they don't plead fraud and they don't argue fraud," Christie told ABC's "This Week," adding that "if you're unwilling to come forward and present the evidence, it must mean the evidence doesn't exist."

Republican Senator Lisa Murkowski tweeted on Sunday that "it is time to begin the full and formal transition process," noting the courts had thus far found Trump's legal claims without merit and that the pressure campaign on state legislators "is not only unprecedented but inconsistent with our democratic process." Critics have said Trump's refusal to facilitate an orderly transition carries serious implications for national security and the fight against COVID-19.

Klain said Biden was being denied intelligence briefings to which he is entitled, FBI background checks on potential Cabinet nominees, and access to agency officials to help develop plans including avoiding delays in COVID-19 vaccine rollout. Jen Psaki, a senior adviser to Biden's transition team, said on CNN's "State of the Union" that legal action to compel the GSA to recognize Biden "isn't our preference."