President-elect Joe Biden is continuing to lay the groundwork for his administration against the backdrop of a resurgence of COVID-19 cases across the United States, while President Donald Trump refuses to accept the election's outcome.
Biden named long-time adviser Ron Klain as his White House chief of staff on Wednesday, his first major appointment since winning the November 3 election.
Klain, who served as president Barack Obama's "Ebola Czar" in 2014 during an outbreak of that virus in West Africa, is expected to take a leading role in the Biden administration's response to the nationwide spike in COVID-19 cases.
Trump's efforts to overturn the election's results in key states have not kept Biden from making preparations to assume office on January 20. The Democrat has spent much of the week huddling with advisers on staffing decisions.
The incumbent, meanwhile, has shown no sign he will concede even as his unproven allegations of widespread voter fraud in key states have met with scepticism from judges and legal analysts.
Since the election was called for Biden by major news organisations on Saturday, Trump has maintained a minimal public schedule, preferring instead to air his grievances on Twitter, and has not addressed the climbing virus caseload nationwide.
The United States as a whole reported more than 1450 COVID-19 deaths on Tuesday, the highest single-day count since mid-August, driving the total death toll above 239,000.
Biden clinched victory on Saturday after being called as winner in a series of battleground states, giving him more than the 270 electoral votes needed in the electoral college that determines who wins the presidency.
Biden is also winning the national popular vote by more than five million votes as a few states still count ballots.
More world leaders have recognised Biden's victory, with Australia, Japan and South Korea joining the list of allies congratulating Biden in phone calls. China and Russia, meanwhile, have held off.
As Trump, the first US president to lose a re-election bid since 1992, desperately tries to cling to power, his administration has resisted co-operating with transition efforts.
Democrats and other critics accuse Trump of aiming to undermine public trust in the US election system and delegitimise Biden's victory through unproven, anecdotal claims of voter fraud.
In Klain, meanwhile, Biden brings in a trusted and experienced operative who also served as vice-president Al Gore's top aide during Bill Clinton's administration.
As Biden's chief of staff during the 2008-09 financial crisis, Klain helped oversee the implementation of the $US787 billion Recovery Act that boosted the then-cratering economy.
"(Klain's) deep, varied experience and capacity to work with people all across the political spectrum is precisely what I need in a White House chief of staff," Biden said in a statement.
While Trump has remained publicly defiant over the election results, he has also been pondering another run for the presidency in 2024.
On Wednesday, he endorsed a top ally, Ronna McDaniel, to remain in her job as the chair of the Republican National Committee - an unusual move for an outgoing president.
In the meantime, Trump's 2020 campaign has brought a new lawsuit in Michigan alleging voter misconduct.
The suit appears unlikely to alter the outcome in the state: he is losing by roughly 148,000 votes in unofficial vote totals.
A Michigan Department of State spokesman said the Trump campaign was promoting false claims to erode public confidence in the election.
Judges have tossed out several Trump lawsuits and legal experts say the litigation has scant chance of changing the outcome.