US President Joe Biden on Monday issued pre-emptive pardons to former Covid-19 advisor Anthony Fauci and retired general Mark Milley to shield them from "politically motivated prosecutions" under the Trump administration.

In an extraordinary move in his last hours in the White House, Biden gave similar pardons to members, staff and witnesses of a US House committee probing the violent January 6, 2021 US Capitol attack by Donald Trump's supporters.

"These public servants have served our nation with honor and distinction and do not deserve to be the targets of unjustified and politically motivated prosecutions," Biden said in a statement.

"These are exceptional circumstances, and I cannot in good conscience do nothing." 

Trump, who will be sworn in on Monday, has repeatedly promised "retribution" against his political opponents and threatened some with criminal prosecution.

Fauci became the face of the country's fight against the Covid pandemic, but his straight-talking takes on the disease in Trump's first term brought him into conflict with the Republican.

It also turned the scientist into a hate figure for many on the right, including Elon Musk, Trump's ally and the world's richest man, who repeatedly called for Fauci to be prosecuted.

Trump was enraged after Milley, who was chairman of the Joint Chiefs of Staff during Trump's first term, told journalist Bob Woodward that Trump was "fascist to the core" and "the most dangerous person to this country."

Milley also revealed that he had secretly called his Chinese counterpart after the Capitol attack to reassure Beijing that the United States remained "stable" and had no intention to attack China.

Trump subsequently wrote on his Truth Social network that "in times gone by, the punishment would have been DEATH!" for Milley.

In a statement, Milley thanked Biden for his executive action.

"I do not wish to spend whatever remaining time the Lord grants me fighting those who unjustly might seek retribution for perceived slights," the former general said.

'Committed no crime'

US media reported that Fauci thanked Biden for the pardon, but stressed "I have committed no crime."

Responding to the report, Trump's son Donald Trump Jr. urged Fauci to turn the pardon down "if he did nothing wrong."

The members of the January 6 committee include fierce Trump critic and former Republican congresswoman Liz Cheney, the daughter of former vice-president Dick Cheney.

"Baseless and politically motivated investigations wreak havoc on the lives, safety, and financial security of targeted individuals and their families," wrote Biden.

The Democrat added that the pardons "should not be mistaken as an acknowledgment that any individual engaged in any wrongdoing, nor should acceptance be misconstrued as an admission of guilt for any offense."

Adam Schiff, a Democrat who was a member of the committee, responded to reports of the pre-emptive pardons being considered in December by saying he would be against such a move.

"I don't think the idea of a blanket pardon of some kind is a good idea," he said at the time.

Trump has regularly complained of being the victim of "lawfare" under the Biden administration, after being criminally prosecuted for offenses including trying to subvert the 2020 election.

Monday's moves were the latest in a slew of pardons and clemencies Biden has granted in his final days in office, including commuting the sentences of nearly 2,500 people in one day — and the controversial pardon of his son Hunter. 

By Danny Kemp