President Bush met with top aides at the White House yesterday morning to discuss a replacement for Supreme Court Justice William J. Brennan Jr., who resigned Friday, and said afterward that he plans to make his first nomination for the high court "as quickly as possible."

A senior official said after the 75-minute session that Bush "wants someone on the court on the first Monday in October," when the next term begins. He predicted the president would make the selection by the end of the week, working from an update of a list developed during his transition.

White House advisers and GOP officials were bracing for a confirmation battle regardless of whom the president nominates. They predicted that Democrats, heading into congressional elections, will try to make the nomination a referendum on abortion even though few observers suggest that this issue alone will determine the nominee's fate.

"The Democrats will try to use this to terrify millions of women on the issue of abortion," an administration source said, "since anyone we nominate will arguably vote to overrule Roe versus Wade." The 1973 ruling declared a constitutional right to abortion and Brennan had been among the dwindling number of justices supportive of Roe.

With his departure, there are now only three votes on the court for Roe. Four justices are clearly hostile to the ruling, and a fifth, Justice Sandra Day O'Connor, is willing to let states impose significant restrictions on abortion and, perhaps, go further.

Supporters and opponents of abortion rights agreed yesterday that the focus of the nomination process will be the candidate's views on abortion rights.

Brennan's departure, warned Kate Michelman, executive director of the National Abortion Rights Action League, "may be the death knell for the right to choose in America." She said that unless Bush selects a candidate with "unequivocal support" for Roe, abortion-rights advocates would launch a campaign similar to the one that helped defeat the nomination of Robert H. Bork in 1987.

"We cannot accept another Anthony Kennedy, whose views seemed to be unclear and therefore was not adjudged to be someone who could be questioned" about his attitude toward Roe at his 1987 confirmation hearings, Michelman said. Justice Kennedy has since consistently voted to uphold abortion restrictions.

But antiabortion groups, an important constituency for Bush, were equally vehement that the president's pledge to choose a nominee who is a "strict constructionist" means that the candidate must be opposed to Roe.

Douglas Johnson, legislative director of the National Right to Life Committee, called the 1973 decision "judicial legislation at its most extreme. Any justice who meets the president's criteria of faithfulness to the real Constitution could not vote to reaffirm Roe v. Wade."

Although few observers expect Bush to choose a candidate who would pass Michelman's test, the vacancy places the president in

a politically precarious situa- tion.

It comes just a year after the court's ruling in Webster v. Reproductive Health Services gave states greater leeway to enact abortion restrictions, and just before a mid-term election in which abortion is expected to play a significant role, and one potentially damaging to Republican candidates.

It also confronts the president at a time when Bush has angered his party's conservative flank by abandoning his "no new taxes" pledge. Conservatives "are adamant," said Robert Billings, legislative director of the American Conservative Union. "They want someone more than just acceptable or not objectionable in abortion. They want someone who is opposed" to Roe.

"After Lithuania, after reneging on the no-taxes pledge, after inviting gays and lesbians into the White House {for a bill-signing ceremony}, after granting trade status to China, this is a chance for Bush to redeem himself with conservatives," Billings said.

At the same time, however, Democratic senators and liberal interest groups signaled that a moderate nominee would avert a replay of the Bork battle. Senate Judiciary Committee Chairman Joseph R. Biden Jr. (D-Del.) urged Bush to "follow the historical practice of consulting with Senate leaders" before making his choice.

"At this historical moment, we call upon President Bush to work closely with Republicans and Democrats and nominate a consensus candidate to the Supreme Court, someone who has consistently demonstrated a commitment to equal justice under the law," said Benjamin Hooks and Ralph G. Neas of the Leadership Conference on Civil Rights, which played a major role in defeating Bork.

Bush, speaking to reporters after the morning meeting, said he reviewed possible candidates with his advisers, but had not made a decision. "It was the first meeting. There will probably be more," he said of the session with White House Chief of Staff John H. Sununu, White House counsel C. Boyden Gray and Attorney General Dick Thornburgh.

White House deputy press secretary Alixe Glen said the president made it clear to his staff "he does not want to see anyone talking on this subject but him." Several officials and outside advisers interviewed yesterday disagreed on the identity of the leading candidates.

"Dan Quayle ought to be a lesson to you all on trying to guess what is in George Bush's mind," said one official. Bush surprised nearly all his advisers when he picked Quayle to be his running mate in 1988. Quayle was almost uniformly dismissed as a serious candidate by Bush advisers during the selection process.

Following the White House meeting, Gray and Thornburgh met at the Justice Department with a small group of department lawyers working on the search process. An administration source said the team worked throughout the day updating background files on a list of 12 to 15 candidates, the vast majority of whom are judges.

"There'd been spadework" done on possible nominees "for quite awhile," the source said, indicating that the selection process could move fairly quickly.

This source added that the list of potential nominees has not been narrowed significantly and that it was premature to focus on any small group.

Among those mentioned most often yesterday by observers, officials and congressional staffers were Solicitor General Kenneth W. Starr and federal appeals court judges Edith H. Jones of Texas and Ferdinand Fernandez of California. Fernandez was recently elevated from district judge, and if approved he would be the first Hispanic on the high court. Some political advisers suggested yesterday that Bush would get the most "external political gain" by naming a "first," much as President Ronald Reagan did when he chose O'Connor, the first and only woman on the high court.

Others mentioned as potential choices included federal appeals court judges Patrick E. Higginbotham of Texas, Pamela A. Rymer of California, Clarence Thomas and Laurence Silberman of the District of Columbia and David H. Souter of Boston. Another possible Hispanic choice was said to be Ricardo Hinojosa, a federal trial judge in Texas.

"Unlike Bork, whom everybody knew was clearly the darling of the far right, this {nomination} is probably not going to receive an overnight reaction one way or the other," said Melanne Verveer of People for the American Way, which played an important role in the battle against Bork.

Some activist conservatives interviewed yesterday strongly supported Jones as a candidate one called "the best choice considering the political calculations involved." He described Jones as "conservative, a strict constructionist {as} Bush said he wanted -- but not way, way over there." Jones, he said, adds the benefit of geography. "She's from Texas and that will help with southern Democrats. When you are a Republican building a confirmation strategy, you count your own and then head straight for the southern Democrats."

Jones was a partner in the Houston law firm in which Secretary of State James A. Baker III once practiced. Although the two are acquainted, Jones and Baker are said to be not particularly close. Officials suggested there is no evidence Baker has weighed in on behalf of Jones or even intends to do so. He has long insisted that he wants to stay out of domestic issues and politics.

One official, who called Starr "certainly a leading candidate if not the leading candidate," suggested nonetheless that Bush may prefer to nominate Starr for a future vacancy. "My gut tells me Bush would like to be bold on this one. Pick someone no one expects. Starr is a good choice but he is so predictable."

A source who advises the White House on politics said the main advice being offered by Republicans is and will be "remember your base" of political support.

The official said that court appointments are the "start-all, end-all, be-all" to conservatives and that selecting someone whom most conservatives can embrace "is vital." But virtually no one believes Bush would renominate Bork. "I believe Bork will never be ruled out because Sununu loves him and why not keep his name out there?" an official said. "But George Bush does not want a Reagan nominee to be his first to the court. He wants his own. And he doesn't want to reopen those wounds. He's got his own of those, too."

Bush advisers said yesterday that although the court nomination is a decision Bush will make on his own, two senior aides are playing key roles.

Gray, the counsel, has been the key official involved in federal judge selection in the administration and, as one official put it, "has the paper, he has the names, he has the records of the judges and knows their judicial philosophies."

Sununu, said the official, "has the politics. What will this gain Bush and the GOP? What are the political upsides and downsides of any choice? Who is pushing and who is fighting whom?"