WASHINGTON - U.S. Supreme Court Justice David Souter plans to retire, giving President Barack Obama his first chance to make an appointment to the nation's highest court, a government official said.

The official, who requested anonymity, confirmed reports late on Thursday by NBC News and National Public Radio that Souter, one of the court's liberal members, would step down.

An appointment by Obama, a Democrat who praised the court's liberal-leaning members during his presidential campaign, would not be likely to shift the court's ideological balance of power.

But Obama could name a younger justice who could serve for decades -- beyond his own presidency even if that turned into two terms, or eight years.

Supreme Court justices are appointed for life. They are the deciding voice on such divisive constitutional issues as abortion rights and the death penalty and the court even decided the U.S. presidential election in 2000.

A spokeswoman for the Supreme Court said Souter, 69, has no comment on these reports that he is planning to resign.

It would be the first Supreme Court justice named by a Democrat since 1994, when President Bill Clinton nominated Justice Stephen Breyer. His successor in the White House, Republican President George W. Bush, named two justices in his eight years in office -- Chief Justice John Roberts and Justice Samuel Alito.

The nine-member court has often split in 5-4 votes between conservative and liberal factions on a range of issues.

The National Public Radio report said Souter was expected to remain on the bench until a successor had been confirmed. The court reconvenes in October after its current term ends in late June.

National Public Radio said Souter has informed the White House of his decision, but a White House aide said on Friday there had not been an official notification.

The president has not received a formal communication from Justice Souter and he deserves the right to make his own announcement, the aide said.

MORE LIBERAL THAN EXPECTED

Chosen for the Supreme Court in 1990 by Republican President George Bush, Souter proved to be far more liberal than initially expected.

He has supported abortion rights, affirmative action programs to help minorities overcome past discrimination and campaign-finance restrictions aimed at political corruption.

Souter also has voted in cases to limit the use of the death penalty and in favor of the legal rights of the prisoners held at the U.S. military base at Guantanamo Bay in Cuba.

Though he is not one of the oldest Supreme Court justices, Souter might have decided he was ready to leave Washington. The fiercely private bachelor, who rarely gives public speeches or attends social functions, has not made a secret of the fact he prefers life in New Hampshire.

Talk that Obama may soon have a chance to name his first Supreme Court justice began earlier this year, when Ruth Bader Ginsburg was diagnosed with pancreatic cancer. But Ginsburg, the sole woman on the court, returned to work after surgery and has said she does not plan to retire any time soon.

Court experts have said Obama is likely to choose a woman as his first nominee. Among the possible candidates are Solicitor General Elena Kagan, the administration's top courtroom lawyer who argues before the Supreme Court; Michigan Gov. Jennifer Granholm and appeals court judges Sonia Sotomayor and Diane Wood.

Picking a Supreme Court nominee would be another major task for Obama, who is already dealing with two wars, the worst recession in decades and efforts in Congress to produce landmark legislation to provide health insurance to all Americans and to curb global warming.

Conservative Republicans may not like the high court nominee chosen by the liberal president, but since the Democrats have a powerful majority in the Senate -- strengthened by the switch to Democrats of Senator Arlen Specter this week -- there may not be much they can do about it.

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