Liberal US Supreme Court Justice Stephen Breyer will retire at the end of the term later this year after nearly three decades on the bench.
His decision ensures President Joe Biden will have an opportunity to nominate a successor who could serve for decades.
But Mr Breyer’s replacement will not shift the court’s current 6-3 conservative majority.
It comes as the court considers several hot-button issues on its docket.
Democrats had been pressuring Mr Breyer – who, at 83, was the oldest justice on the bench – to retire so they could fill the seat while they retained control of the White House and Senate.
Mr Biden has previously pledged to nominate a black woman to the court for the first time.
Ketanji Brown Jackson, 51, a former law clerk to Mr Breyer, is believed to be the top contender for the job. Ms Jackson was confirmed last June to a seat on the US Circuit Court of Appeals for the District of Columbia, in which she succeeded current Attorney General Merrick Garland.
Leondra Kruger, 45, who serves on the California Supreme Court, is another possibility.
In a statement, the top Democrat in the Senate called the outgoing Mr Breyer “a model jurist”.
“President Biden’s nominee will receive a prompt hearing in the Senate Judiciary Committee, and will be considered and confirmed by the full United States Senate with all deliberate speed,” said Senator Chuck Schumer.
The White House declined to comment on the news.
Each of the nine judges – known as justices – serves a lifetime appointment after being nominated by the president and approved by the Senate.
The court plays a key role in American life and is often the final word on highly contentious laws, disputes between states and the federal government, and final appeals to stay executions.
Appointed to the court in 1994 by President Bill Clinton, Mr Breyer was among its most consistent liberal voices.
He has expressed concern over the increasing politicisation of the court, telling an audience in 2021 that “it is wrong to think of the court as another political institution”.
A welcome respite for Joe Biden
Anxious liberals who have endured a string of Supreme Court disappointments in recent years can exhale, at least for a moment. Liberal justice Stephen Breyer is going to retire, giving Joe Biden the chance to name a replacement that can be confirmed while Democrats control the US Senate.
The move won’t alter the conservative tilt of the high court, which Donald Trump cemented with three appointments in four years. It will, however, ensure Mr Breyer will be replaced by someone who could conceivably hold the seat for decades.
The confirmation process to fill the vacancy should provide a welcome respite for a president who has been buffeted by legislative defeats and bad domestic and international news in recent months.
If all goes smoothly – admittedly, no guarantee – the choice has the potential to remind liberals why having a Democrat in the White House is important and culminate in a Senate vote with a rare (for this president) successful outcome.