US President Joe Biden on Monday issued preemptive pardons to former medical advisor Anthony Fauci, retired general Mark Milley, and members, staff and witnesses of a House committee investigating the US Capitol attack of January 6, 2021.

"These are exceptional circumstances, and I cannot in good conscience do nothing," Biden said in a statement released hours before he leaves office.

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

The pardons will effectively protect several outspoken critics of President-elect Donald Trump, many of whom he has openly vowed to prosecute. 

Milley served as chairman of the Joint Chiefs of Staff during Trump’s first term as president and has called Trump a "fascist". 

Fauci was director of the National Institute of Allergy and Infection Disease for several decades and came to public prominence during the COVID-19 pandemic.

Biden said the pardons did not mean the beneficiaries were guilty of any crime. 

Biden, in his statement, noted that the pardons did not denote guilt.

“The issuance of these pardons should not be mistaken as an acknowledgement that any individual engaged in any wrongdoing, nor should acceptance be misconstrued as an admission of guilt for any offence. Our nation owes these public servants a debt of gratitude for their tireless commitment to our country,” he wrote.