When President Reagan announced his ill-fated nomination of Robert H. Bork to the Supreme Court during the summer, Sen. John W. Warner (R-Va.) quickly jumped out in front, declaring Bork a man "of unquestioned integrity" and confidently predicting that Bork would win Senate confirmation.

Yet as the Senate prepares this week to debate and vote on Bork's nomination -- with his rejection a foregone conclusion -- Warner is one of only nine senators who has yet to declare publicly how he will vote.

Warner said yesterday he will reserve judgment until the floor debate is concluded, "out of respect" for Bork and the traditions of the Senate and to give himself more time to study the Judiciary Committee's reports on the long nomination hearings.

"If all 100 senators were to indicate before the floor debate how they intended to vote, the floor debate would be virtually eclipsed of any importance, and that would be a failing of our constitutional responsibility," he said.

But others say Warner's reluctance to take a stand reflects the intense conflicting pressure he is under from Virginia's conservative Republican Party, which supports Bork, and the state's increasingly influential black leadership, which has made opposition to Bork a civil rights litmus test.

Warner got 25 percent of the black vote in his reelection bid in 1984 -- a remarkable showing for a Republican in a statewide office -- and has received high praise from black leaders for gaining the appointment of Virginia's first black federal judge, James R. Spencer. Those political gains could be wiped out if Warner votes for Bork.

"A vote for Bork would undo a great deal of the good will he has created among the black citizens of Virginia," Charles Mangum, a Lynchburg lawyer and president of Virginia's branch of the NAACP, said yesterday.

"It's one thing to say, 'I'm fair and impartial and I'm looking out for your best interests,' " Mangum said in describing Warner's deliberations. "It's another thing to put a gunslinger like Bork in your midst who might shoot you down at any possible minute."

A Democratic House member from Virginia, who declined to be identified, agreed that Warner would "alienate a large percentage of black voters" by voting for Bork. At the same time, he said, Virginia conservatives view the vote as a "loyalty test."

"I'm sure he wasn't pleased when Judge Bork announced he was going to stay in the contest," the representative said.

Warner's dilemma is not unique. Other conservative Southern senators have been heavily swayed by the lobbying efforts of civil rights groups, and their widespread opposition has played a key role in sinking Bork's nomination.

Virginia Democratic Party Chairman Lawrence Framme III, who normally delights in the political woes of state Republicans, said he was fairly sympathetic to Warner's plight.

"The vote on Bork is a difficult decision," Framme said. "It's not a clear-cut decision either way."

Sen. Paul S. Trible Jr. (R-Va.), who is not seeking another term, announced on July 1 that he will support Bork. Maryland's two Democratic senators, Paul S. Sarbanes and Barbara A. Mikulski, have announced they will vote against Bork.

Stephen Haner, a spokesman for the Virginia Republican Party, voiced confidence that Warner would vote for Bork, despite the problems he might encounter with Virginia blacks.

"If Warner were up for reelection next year, that's one thing," Haner said. "But he's not up until 1990. I don't know whether, come 1990, the NAACP and the black vote would be so angry about the vote that he need fear it . . . . He has three years to make it up to them."

Warner, 60, a former Navy secretary, was elected to a second term in 1984, defeating Democrat Edythe C. Harrison with 70 percent of the vote. As the ranking Republican on the Senate Armed Services Committee, Warner has carefully protected the interests of Virginia -- a major beneficiary of defense spending -- while advocating a strong national defense. Republican and Democrats agree that he has a strong political base and would be extremely difficult to unseat.

Still, Warner's office has been feeling the heat of the well-orchestrated anti-Bork movement, led by the Leadership Conference on Civil Rights, the American Civil Liberties Union and the NAACP.

Warner, the only Southern Republican who has yet to take a stand on Bork, stressed that he had been tied up for weeks in the debate over the fiscal 1988 defense authorization bill and has had little time to focus on the nomination.

Sen. Sam Nunn (D-Ga.), the chairman of the Armed Services Committee who stood side by side with Warner during the 100 hours of debate over the defense bill, is one of only three Democrats who has not announced his position on Bork. Warner and Nunn have developed a close working relationship, and some observers believe Nunn could influence Warner's decision.

"I'm approaching this decision purely on the basis of the qualifications of this man to be a public servant of the people," Warner said. "While I value the various communications from Virginians and groups . . . I am not going to be guided by any political considerations whatsoever."

"I don't particularly envy my being {in this position}," Warner said as an afterthought. "I didn't want to be one of the last few. But I feel very strongly about the need for a debate."