WASHINGTON - (AP) - Supreme Court Justice John Paul Stevens, thecourt's oldest member and leader of its liberal bloc, is retiring.President Barack Obama now has his second high court opening tofill.

Stevens said Friday he will step down when the court finishesits work for the summer in late June or early July. He said hehopes his successor is confirmed "well in advance of thecommencement of the court's next term."

Stevens' announcement leaves ample time for the White House tosettle on a successor and for Senate Democrats, who control a59-vote majority, to hold confirmation hearings and a vote beforethe court's next term begins in October. Republicans have not ruledout attempts to delay confirmation.

Stevens' announcement had been hinted at for months. It comes 11days before his 90th birthday.

Throughout his tenure, which began after President Gerald Fordnominated him in 1975, Stevens usually sided with the court'sliberal bloc in the most contentious cases - those involvingabortion, criminal law, civil rights and church-state relations. Heled the dissenters as well in the case of Bush v. Gore that sealedPresident George W. Bush's election in 2000.

Stevens began signaling a possible retirement last summer whenhe hired just one of his usual complement of four law clerks forthe next court term. He acknowledged in several interviews that hewas contemplating stepping down and would certainly do so duringObama's presidency.

Chief Justice John Roberts said in a written statement thatStevens "has enriched the lives of everyone at the Court throughhis intellect, independence, and warm grace."

Senate confirmations of Supreme Court justices have increasinglybecome political battles and this one will come amid the added heatof congressional election campaigns.

Sen. Patrick Leahy, D-Vt., chairman of the Senate JudiciaryCommittee, appealed for civility. "I hope that senators on bothsides of the aisle will make this process a thoughtful and civildiscourse," Leahy said.

Looking toward those hearings, Senate Republican Leader MitchMcConnell of Kentucky said, "Americans can expect SenateRepublicans to make a sustained and vigorous case for judicialrestraint and the fundamental importance of an evenhanded readingof the law."

Stevens informed Obama in a one-paragraph letter addressed to"My dear Mr. President." It was delivered to the White House bycourt messenger at 10:30 a.m. EDT, two minutes before the court'spublic announcement. The news came on a day when the court wasn'tin session.

White House counsel Bob Bauer telephoned the news to Obama onAir Force One, as he returned from a trip to Prague.

The leading candidates to replace Stevens are Solicitor GeneralElena Kagan, 49, and federal appellate Judges Merrick Garland, 57,in Washington and Diane Wood, 59, in Chicago.

Stevens' departure will not change the court'sconservative-liberal split because Obama is certain to name aliberal-leaning replacement, as he did with his first nominee,Justice Sonia Sotomayor. But the new justice is not likely to beable to match Stevens' ability to marshal narrow majorities in bigcases.

Stevens was able to draw the support of the court's swing votes,now-retired Justice Sandra Day O'Connor and Justice AnthonyKennedy, to rein in or block some Bush administration policies,including the detention of suspected terrorists following the Sept.11, 2001, attacks, its tilt toward protecting businesses from somelawsuits and its refusal to act against global warming.

But after the arrival of Roberts and Justice Samuel Alito,President George W. Bush's appointees, Stevens more often was amongthe four liberal justices in dissent.

Stevens' recent dissent in a major case involving campaignfinance laws showed both the eloquence of his writing and, in hisstumbling reading of his opinion in the courtroom, signs that hisage might at long last be affecting him, though he remains anactive tennis player and swimmer.

He is the court's last World War II veteran and that experiencesometimes finds its way into his writings, recently in a referenceto Tokyo Rose, the English-speaking Japanese radio announcer whoaddressed U.S. soldiers in the Pacific.

Stevens had a reputation as a bright and independent federalappeals court judge when Ford, acting on a recommendation byAttorney General Edward Levi, nominated him to the Supreme Court. His friendly manner of questioning lawyers who appeared beforethe court could not hide Stevens' keen mind. His questions oftenzero in on the most telling weaknesses of a lawyer's argument andthe case's practical effect on everyday people.

A pleasant, unassuming man, Stevens has been a prolific andlucid writer. For many years, he wrote more opinions each courtterm than any other justice.

Most justices let their law clerks write the first drafts ofopinions, but Stevens has used his clerks as editors. He'd write the first draft and submit it to the clerks forcomment. "That's when the real fun begins," Stevens once told avisitor. "The give and take can get pretty fierce."

As a result, his opinions have reflected his personal writingstyle - a conversational one that contrasted sharply with the dry,dull efforts of some other justices.

He said recently that one sign that it would be time to retirewould be an inability to churn out those first drafts. But heinsisted in recent days that he was still writing them.