President Joe Biden plans on Friday to nominate Ketanji Brown Jackson, a federal appellate judge, to become the first Black woman to serve on the U.S. Supreme Court.

Jackson, 51, would replace liberal Justice Stephen Breyer, who she once clerked for. Breyer announced in January his intention to step down.

The White House said in a statement that Biden was looking for a candidate with "exceptional credentials, unimpeachable character and unwavering dedication to the rule of law."

"He also sought a nominee — much like Justice Breyer — who is wise, pragmatic and has a deep understanding of the Constitution as an enduring charter of liberty," the statement said.

"And the president sought an individual who is committed to equal justice under the law and who understands the profound impact that the Supreme Court's decisions have on the lives of the American people."

The timing of Biden's announcement has been in flux because of Russia's invasion of Ukraine.

The announcement of Jackson, expected to take place at the White House, will tee up a confirmation battle in a Senate in which the Democrats enjoy the narrowest of margins.

The Senate voted 53-44 last year to confirm Jackson after Biden nominated her to the influential U.S. Court of Appeals for the District of Columbia Circuit, with Republican senators Lindsey Graham, Susan Collins and Lisa Murkowski voting in favour.

At Jackson's confirmation hearing last year, some Republicans questioned her on whether race plays a role in her approach to deciding cases. She said it did not.

"I've experienced life in perhaps a different way than some of my colleagues because of who I am," Jackson said.

In her short time on the appeals court, she has authored two majority opinions, including one in favour of public sector unions challenging a regulation issued during Republican former President Donald Trump's administration that restricted their bargaining power.

Reaction from Democratic Senate Majority Leader:

She was part of a three-judge panel that ruled in December against Trump's bid to prevent White House records from being handed over to the House of Representatives committee investigating the Jan. 6, 2021, attack on the Capitol by a mob of his supporters. The Supreme Court last month declined to block that decision.

The Senate previously confirmed her as a federal district judge, a job she held for eight years.

Democrats would welcome any Republican votes

If confirmed to the top court, Jackson would be the third Black justice, after Thurgood Marshall (1967-1991) and Clarence Thomas, the conservative jurist who has been on the bench since 1991.

Jackson would become the sixth woman ever to serve on the Supreme Court, joining current members Amy Coney Barrett, Elena Kagan and Sonia Sotomayor, the retired Sandra Day O'Connor and the late Ruth Bader Ginsburg.

U.S. Supreme Court Justice Stephen Breyer speaks at the White House on Jan. 27 while President Joe Biden looks on. Brown Jackson could potentially replace Breyer, for whom she once served as a clerk. (Kevin Lamarque/Reuters)

"Everyone should be represented," Biden said after Breyer announced his intention to step down. "We talked about the Supreme Court -- I'm looking forward to making sure there's a black woman on the Supreme Court to make sure we in fact get everyone represented."

The Supreme Court has a 6-3 conservative majority that will be unchanged by the new appointment. But it could given Biden a chance to shore up political support among women, minorities and liberals ahead of the Nov. 8 midterm elections in which Democrats are fighting to retain control of both chambers of Congress.

Jackson would join the liberal minority of a conservative-dominated court that is weighing cutbacks to abortion rights and will be considering ending affirmative action in college admissions and restricting voting rights efforts to increase minority representation.

Reaction from Republican Senate Minority Leader reacts:

Democrats hold the majority by a razor-thin 50-50 margin with Vice-President Kamala Harris as a potential tiebreaker in a confirmation vote. There was also concern in the party when New Mexico Sen. Ben Ray Lujan suffered a stroke last month, with his return believed to be weeks away.

Jackson was born in Washington, D.C., but raised in Miami. She attended Harvard University, graduating from its law school in 1996.

Jackson in 2020 paid tribute to Breyer during a virtual conference in which they both participated, saying he "opened doors of opportunities" not just through his judicial decisions but also by hiring a diverse group of law clerks.

"As a descendant of slaves," Jackson said, "let me just say that, Justice [Breyer], your thoughtfulness in that regard has made a world of difference."

Jackson worked from 2002 to 2004 for Kenneth Feinberg, the lawyer known for overseeing compensation programs including one for victims of the Sept. 11, 2001, attacks on the United States.

From 2005 to 2007 she served as a court-appointed lawyer paid by the government to represent criminal defendants who could not afford counsel. Among her clients was an Afghan detainee held at the U.S. naval base at Guantanamo Bay, Cuba

She also had two separate stints at the U.S. Sentencing Commission, which issues guidance to judges on criminal sentencing, including a four year stint starting in 2010 as the Senate-confirmed vice-chair.