Flynn pardoned

The president followed up by pardoning former national security adviser Michael Flynn, the second Trump associate granted clemency among those convicted in a probe into alleged Russian interference in the 2016 election. Moscow has denied claims of meddling.

For his part, Biden has largely projected serenity as the necessary elements of a presidential transition - money, access to office space and more - were held at bay for nearly three weeks by Trump's tactics and a delayed ascertainment by the General Services Administration that he had won the Nov 3 election.

Biden pledged more virus testing, more protective gear and clearer guidance for businesses and schools to reopen when he becomes president. Until vaccines are distributed, he said, masks, social distancing and limits in the size of gatherings "are our most effective tools to combat the virus".

Biden's remarks came as COVID-19 cases surge nationwide. Hospitalizations, deaths and the testing positivity rate were also up sharply as the nation headed into Thanksgiving, and public health experts have warned that the large family gatherings expected for the holiday are likely to extend and exacerbate the surge.

He has formed a coronavirus advisory board of scientists, doctors and public health experts, and plans to establish a COVID-19 coordinator in the White House to lead his administration's response.

This week, however, Biden focused beyond the crisis at home and unveiled his national security team on Tuesday, including his nominees for secretary of state and director of national intelligence. Drawing implicit contrasts with Trump, Biden said the team "reflects the fact that America is back, ready to lead the world, not retreat from it". He is also expected to name Janet Yellen as Treasury secretary in the coming weeks.

Agencies and Ai Heping in New York contributed to this story.