U.S. Supreme Court Justice Stephen Breyer has said he will retire on his own terms amid calls from progressives for him to step down from the court so President Biden can name a younger liberal to take his place.

"I'm only going to say that I'm not going to go beyond what I previously said on the subject, and that is that I do not believe I should stay on the Supreme Court, or want to stay on the Supreme Court, until I die," he told NPR's legal affairs correspondent Nina Totenberg in an interview in Boston to promote his book, The Authority of the Court and the Peril of Politics. "And when exactly I should retire, or will retire, has many complex parts to it. I think I'm aware of most of them, and I am, and will consider them."

Breyer's remarks, while not a surprise — he hired four clerks in July for the court's next term — are likely to anger progressive activists who believe that the 83-year-old justice should make way for a younger nominee who holds his — and their — values and views. They want him to step down while Democrats still narrowly control the Senate and before the 2022 midterms, when control of the chamber is at stake.

Progressives fear a replay of the situation following the death in September 2020 of 87-year-old Justice Ruth Bader Ginsburg, which allowed President Donald Trump to nominate — and for the Republican-controlled Senate to quickly confirm — Amy Coney Barrett, giving conservatives a 6-3 supermajority on the Supreme Court. Ginsburg didn't step down in 2014 when both the presidency and the Senate were in the hands of Democrats.

But Breyer said being in the court's minority didn't deter him because "about half of our opinions, almost half, are almost always unanimous."

"I see it as trying to decide this case and trying to decide the next case," he said. "And we might be the greatest of friends ... and allies beyond belief on Case 1, and Case 2, we might be on absolute opposite sides."

But an NPR analysis of the court's last term found that the justices swerved to the right, even by the standards of the traditionally conservative Roberts court. While there was unanimity on statutory matters, the justices split along ideological lines in the high-profile politically charged cases — such as voting rights.

Supreme Court justices are appointed for life, but a justice can decide to retire at any time. Progressives had hoped to push Breyer in that direction. One group, Demand Justice, even sent a billboard truck driving around the Supreme Court building in April with the message: "Breyer, retire. It's time for a Black woman Supreme Court justice," a reference to the president's vow to nominate a Black woman to the court.

The campaign to push for Breyer's retirement has not gained momentum in the Senate, which votes on judicial nominations. Only a handful of Democrats have suggested they would like to see Breyer, who was nominated to the court in 1994 by President Bill Clinton, retire of his own accord.

The White House has said that Biden's view is that retirement decisions are up to justices themselves.

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