The reports suggest Trump's condition was far more serious than how it was portrayed to the public by White House officials and doctors.

The National Guard said in a statement that it would not discuss coronavirus cases, but personnel were following Centers for Disease Control and Prevention guidelines.

The White House announced the abrupt change in the president's schedule late Wednesday.

On Thursday, House Democrats who also favour $2,000 checks will all but dare Republicans to break with Trump, calling up his proposal for a Christmas Eve vote.

Essential personnel at the White House and certain officials in all three branches of government were to be vaccinated within the next 10 days, said a Reuters source

Dr. Scott Atlas, a Stanford University neuroradiologist who had no formal experience in public health or infectious diseases, resigned at the end of his temporary government assignment.

U.S. President Donald Trump has miscast or exaggerated the military's role in the crash program to accelerate the development, production and eventual distribution of COVID-19 vaccines.

Dr. Moncef Slaoui, chief scientific adviser for "Operation Warp Speed," sketched out a timeline for getting the initial doses.

The spokesman says the younger Trump learned his diagnosis earlier this week, has no symptoms and has been quarantining.

Biden also said business and labor leaders had signalled willingness to cooperate to fix the pandemic-battered U.S. economy but stressed COVID-19 first must be brought under control and urged Congress to pass relief legislation.