This Nov 21, 2020 photo shows US Democrat Joe Biden (center) leaving St. Ann Parish in Wilmington, Delaware. (ALEX BRANDON / AP)

WILMINGTON - US Democratic presidential nominee Joe Biden is moving forward on his campaign pledge to restore the United States as a leader on the global stage and lean on experts, tapping veteran diplomats for key posts even as President Donald Trump continues to refuse to concede.

Biden will name Antony Blinken as secretary of state and Linda Thomas-Greenfield as ambassador to the United Nations, bringing deep foreign-policy backgrounds to the nascent administration while providing a sharp contrast with Trump, who distrusted such experience and embraced an "America First" policy that strained longstanding US relationships.

Blinken could be named as early as Tuesday, according to sources close to Biden, while Axios first reported Thomas-Greenfield's impending nomination.

Antony Blinken served as No 2 at the State Department and as deputy national security adviser in former president Barack Obama's administration

Blinken's appointment made another longtime Biden aide and foreign policy veteran, Jake Sullivan, the top candidate to be US national security adviser, a source said. 

During the campaign, Biden severely criticized Trump's go-it-alone foreign policy and pledged to recommit to NATO and other global pacts, while promising to tap experts to fight the COVID crisis and other problems at home. He has promised to rejoin the Paris Climate Accord and the World Health Organization and potentially the Iran nuclear deal.

“America First has made America alone,” Biden said in a town-hall meeting in October.

Blinken is a longtime Biden confidant who served as No 2 at the State Department and as deputy national security adviser in former president Barack Obama's administration, in which Biden served as vice-president.

In this Sept 29, 2016 file photo, then Deputy Secretary of State Antony Blinken testifies on Capitol Hill in Washington before the Senate Foreign Relations Committee hearing on Syria. (JOSE LUIS MAGANA / AP)

Thomas-Greenfield, a Black woman who served as the assistant secretary of state for Africa under Obama, was intended to restore morale and help fulfill Biden’s pledge to choose a diverse cabinet, Axios reported.

Sullivan served as Biden's national security adviser during the Obama administration and also as deputy chief of staff to Secretary of State Hillary Clinton.

Jake Sullivan is said to be the top candidate for national security adviser while former Fed chair Janet Yellen is believed to be the top candidate for treasury secretary

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.

Biden said last week he had chosen a Treasury secretary, and would announce the winner near Thanksgiving, which falls on Nov 26. Former Federal Reserve chief Janet Yellen is said to be the top candidate.

A spokesman for Biden's transition team declined to comment.

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.

Biden was projected to have won the presidential election on Nov 3 and is expected 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 declared victory, 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.

ALSO READ: Pennsylvania court loss sets back Trump bid to overturn poll

Attempts to thwart certification of vote tallies have failed for Trump thus far in courts in Pennsylvania, Georgia, Michigan and Arizona, with Pennsylvania dealing the latest blow after a district judge dismissed the lawsuit on Saturday

Biden was projected to have 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

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.

READ MORE: Trump's reversal snuffs out poll shift

US President Donald Trump drives a golf cart during a golf session at Trump National Golf Club in Sterling, Virginia, on Nov 22, 2020. (MANUEL BALCE CENETA / AP)

Attempts to thwart certification of vote tallies have failed thus far in courts in Pennsylvania, Georgia, Michigan and Arizona. US 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

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 US Circuit Court of Appeals. Pennsylvania is expected to send its county results to its top election official for certification on Monday.

Michigan is also set to certify its results Monday.

Pennsylvania and Michigan are expected to certify their results Monday. Trump's bid of overturning the election will be doomed if the certifications confirm Biden as the winner of a combined 36 electoral votes

Trump's bid of overturning the election will be doomed if Michigan and Pennsylvania certify their results, confirming Biden as the winner of a combined 36 electoral votes. 

It remains unclear whether the process in Michigan will work as state law dictates. Michigan's canvassing board, which is evenly split between two Democrats and two Republicans, will meet on Monday to decide whether to certify the results.

A deadlock on moving ahead with certification would likely force the matter into state appeals courts, where an order would be sought to compel the board to perform its function. If the members refused, Governor Gretchen Whitmer, a Democrat, has the authority to replace them.

Ahead of Monday's vote by Michigan's canvassing board, Republican National Committee Chairwoman Ronna McDaniel, a Trump ally, and Michigan Republican Party Chairwoman Laura Cox wrote a letter urging the board to conduct an audit before certification.

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'

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."

Critics have warned Trump's refusal to facilitate an orderly transition carries serious implications for national security and the fight against COVID-19

"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.

READ MORE: Biden's advisers warn transition delay could hinder virus fight

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."