US President Joe Biden reiterated his intention to nominate a black woman to be the first to the Supreme Court, the highest US judicial body, in a move he described as "too late."

Biden said Thursday that he plans to select a black female judge by the end of February to succeed retired Supreme Court Justice Stephen Breyer.

Breyer, 83, formally announced his retirement in a letter to Biden unveiled Thursday, saying he plans to retire at the end of the Supreme Court's current term, which usually runs until the end of June.

The Democrats - to whom Biden belongs - have a very small majority in the Senate, which the US Constitution requires that certifies the appointment of candidates to the Supreme Court.

"It's a happy and sad day for me," Biden said, during his appearance with Judge Breyer at the White House, noting that he had known Breyer since the seventies.

Biden said he had made no decision on who would succeed Breyer, except that a woman with exceptional qualifications would take over, and said she would be the first black woman ever to be nominated for the United States Supreme Court.

Biden had promised in his election campaign that he would appoint the first black woman to the Supreme Court as soon as a seat on the nation's highest judicial body became available.

Breyer's retirement after 27 years of service provides Biden's first opportunity to fill a void in the nine-member court, in which the majority of its conservative judges - 6 to 3 - have shown an increasing determination to reformulate laws on several issues, including abortion and the right to bear arms.

Biden's predecessor, Republican President Donald Trump, was able to appoint 3 judges during his four years in office.