Washington DC - Outgoing President Joe Biden said Thursday he had commuted the sentences of nearly 1,500 people and pardoned 39 others, in what the White House called the largest single-day act of clemency in US history.

"America was built on the promise of possibility and second chances," Biden said. "As President, I have the great privilege of extending mercy to people who have demonstrated remorse and rehabilitation."

Biden said the 39 people pardoned for non-violent crimes "have shown successful rehabilitation and have shown commitment to making their communities stronger and safer."

The White House said the nearly 1,500 people granted commuted sentences – "the most ever in a single day" – had been serving them at home for at least one year.

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"These commutation recipients, who were placed on home confinement during the Covid pandemic, have successfully reintegrated into their families and communities and have shown that they deserve a second chance," Biden said.

Biden this month faced criticism for issuing an official pardon for his son Hunter, who was convicted and was due to be sentenced on gun and tax charges, despite promising that he would not intervene in his son's legal troubles.

Hunter Biden pleaded guilty in a tax evasion trial in September and was facing up to 17 years in prison. For the separate gun charge, he was facing 25 years in prison.

The White House said among those getting relief from the president on Thursday included a "a decorated military veteran and pilot who spends much of his time helping his fellow church members."

A nurse "who has led emergency response for several natural disasters" and an addiction counsellor "who volunteers his time" were also singled out for relief.

"Together, these actions build on the President's record of criminal justice reform to help reunite families, strengthen communities, and reintegrate individuals back into society," the White House said.

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"The President has issued more sentence commutations at this point in his presidency than any of his recent predecessors at the same point in their first terms."

Even after Thursday's announcement, Biden still has more than 10,000 clemency requests on his desk. Advocacy organizations, federal lawmakers, and past clemency recipients have urged him to use his powers to leave behind a positive legacy, including by commuting the death sentences of more than three dozen people before Donald Trump takes office.

Among the most high-profile cases is that of imprisoned Indigenous freedom fighter Leonard Peltier, who has spent almost half a century behind bars despite widespread doubt over his conviction.

On Monday, Biden said he was "looking at" the possibility of freeing Peltier.