White House press secretary Jen Psaki on Friday indicated President Biden would leave it up to Supreme Court Justice Stephen Breyer to determine when to retire amid mounting pressure from progressive groups.

"He believes that’s a decision Justice Breyer will make when he decides it’s time to no longer serve on the Supreme Court,” Psaki told reporters, adding that she was not aware of any conversations between Biden and Supreme Court justices since his inauguration.

Demand Justice, an advocacy group led by a former top aide to Senate Majority Leader Charles Schumer (D-N.Y.), launched an effort Friday to push Breyer, 82, to step down so that Biden can appoint the first Black woman to serve on the Supreme Court while Democrats have control of the Senate.

“We are now firmly in the window when past justices have announced their retirement, so it's officially worrisome that Justice Breyer has not said yet that he will step down. The only responsible choice for Justice Breyer is to immediately announce his retirement so President Biden can quickly nominate the first-ever Black woman Supreme Court justice,” said Brian Fallon, the executive director of Demand Justice and a former top aide to Schumer.

Demand Justice has hired a billboard truck to drive around the Supreme Court with the message: “Breyer, retire. It’s time for a Black woman Supreme Court justice. There’s no time to waste."

The group also launched an online petition asking signatories to “Tell Justice Breyer: Put the country first. Don’t risk your legacy to an uncertain political future. Retire now.’”

Progressives are still reeling from the death of Ruth Bader Ginsburg, a liberal icon who died in September, allowing then-President Trump and the GOP-controlled Senate to fill her seat with a conservative justice. 

Ginsburg, who was 87 when she died, continued serving despite various health ailments. Some Democrats had urged her to consider stepping down while former President Obama was still in office so that he could choose her replacement.

Demand Justice launched its new effort to pressure Breyer on the same day Biden issued an executive order establishing a committee to study the expansion of the Supreme Court, something progressives have pushed for in recent years as the court shifts to the right but that the president has not explicitly said he favors or opposes.

The White House said that the commission will hold public meetings to hear arguments from experts and interested parties. It will be required to complete a report on its work within 180 days of its first public meeting.