In the interview, the outgoing president also defended the full and unconditional pardon he issued to his son, Hunter Biden, who was facing sentencing for two criminal cases - tax evasion and illegally buying a gun - despite repeatedly insisting he would not do so.

Biden, who first came to Capitol Hill in 1972 as a US senator, drew criticism from his own party over his apparent reluctance to drop out of the presidential race amid concerns over his age and mental acuity.