President Joe Biden promised voters that he would name progressives to the Supreme Court if he wins a second term this November and suggested there might be two openings on the bench.

The president was speaking in Philadelphia on Wednesday as he and Vice President Kamala Harris kicked off a national outreach program to mobilize Black voters, clicking off accomplishments of his first term, including putting Justice Ketanji Brown Jackson on the high court.

"The next president - they're going to be able to appoint a couple of justices, and I'll be damned if they're not going to ... if in fact we're able to change some of the justices when they retire and put in really progressive judges like we've always had, tell me that won't change your life," he told the crowd, recalling the court's decision in 2022 to overturn Roe v. Wade.

Former President Donald Trump appointed three justices - Brett Kavanaugh, Amy Coney Barrett and Neil Gorsuch - to create a 6-3 conservative majority on the court.

Two of the current justices are over 70 - Clarence Thomas, 75, and Samuel Alito, 73.

Sonia Sotomayor turns 70 next month.

Biden named Brown Jackson to fill the vacancy created by the retirement of 83-year-old Justice Stephen Breyer in 2022.