US President Joe Biden is commuting the sentences of nearly 2,500 people convicted of non-violent drug offences, three days before he leaves office.

Biden said the offenders were "serving disproportionately long sentences compared to the sentences they would receive today under current law, policy, and practice" and his action would right "historic wrongs".

In an announcement on Friday, Biden said he had now issued more individual pardons and commutations "than any other president in US history".

The news comes after the outgoing president commuted the sentences of 37 of 40 federal death row inmates and issued a wave of commutations and pardons in December, including for his son Hunter Biden.

The president said Friday's clemency action affected individuals "who received lengthy sentences based on discredited distinctions between crack and powder cocaine, as well as outdated sentencing enhancements for drug crimes".

When a US Senator, he had crafted a 1986 law that set this sentencing disparity, but backed ditching the guidelines, which happened in 2022.

He said on Friday that Congress, through laws in recent years, had recognised "it is time that we equalise these sentencing disparities".

The president's changed perspective over his decades as an elected official reflects how attitudes on the US "war on drugs" - which saw strict sentences imposed for drug crimes, particularly on racial minorities, starting in the 1970s - have evolved.

"This action is an important step toward righting historic wrongs, correcting sentencing disparities, and providing deserving individuals the opportunity to return to their families and communities after spending far too much time behind bars," the president said on Friday.

"I am proud of my record on clemency and will continue to review additional commutations and pardons."