NEW YORK, JULY 9 -- White House Chief of Staff Howard H. Baker Jr. today called on the NAACP not to "precipitously oppose" the Supreme Court nomination of conservative Judge Robert H. Bork before confirmation hearings begin.

Baker, the highest-ranking member of the Reagan administration to address the civil rights group during its six-day meeting here this week, said the NAACP should listen to Bork's defenders before they decide to join his detractors.

Baker's defense of Bork here came as White House officials in Washington and Republicans in the Senate continued sparring with Democrats over Bork's confirmation hearings which Senate Judiciary Committee Chairman Joseph R. Biden Jr. (D-Del.) said will begin Sept. 15.

Presidential spokesman Marlin Fitzwater, asked about Biden's statement on Wednesday that he would almost certainly oppose the Bork nomination, said, "I think it's regrettable that he has choosen to politicize the hearings in this kind of partisan fashion."

Fitzwater also said it is "regrettable" that the nomination will not be considered by the full Senate before the court term opens in October, "though we are hopeful they will reconsider," and he noted that Republican congressional leaders are asking that the hearings start sooner.

Despite Baker's appeal, NAACP members had earlier agreed to oppose Bork, and yesterday cheered and gave a standing ovation after Baker said he was "well aware of the fact that most members of this organization are opposed to the confirmation of Judge Bork to the Supreme Court."

"I ask you today not to judge Robert Bork upon a fragmented record, reflected in newspaper clippings," Baker told the delegates. "I ask you to consider the full record and Judge Bork's views as they emerge during the confirmation process."

Baker said afterward that he was "determined" to defend Bork's record before the NAACP, which has heard speeches from four presidential candidates this week denouncing the U.S. Appeals Court judge as a threat to civil rights of minorities and women and as an ideologue who will alter the balance of the court.

"As an organization that prides itself on fairness, as individuals who have been victims of prejudice based upon race, I am sure that you understand the importance of allowing all the facts to be put forward in a nonheated or emotional fashion, particularly as the Senate . . . affords Justice Bork an opportunity to be heard, examined and confirmed," Baker said.

The Bork nomination, which has overshadowed other issues at what has become an overtly political convention, also drew comment today from presidential candidate Sen. Albert Gore Jr. (D-Tenn.).

Gore was the only candidate appearing at the convention this week who did not denounce Bork outright, saying only that he has "reservations" about the nomination.

"I have a personal view that leads me to await the conclusion of the hearings before making a formal judgment on how I will vote," Gore told reporters.

But he added that it is the NAACP's duty to oppose the Bork nomination if it sees fit and refused to criticize Biden for his decision to oppose Bork when confirmation hearings begin in September.

NAACP executive director Benjamin L. Hooks said he talked with Baker before his speech today and warned him that this was an "anti-Bork convention."

"Although I don't agree with his views on Bork, I respect them," Hooks said.

On Capitol Hill, Senate Republican leaders pressed the Democratic majority to agree to a specific date for the Judiciary Committee vote on the Bork nomination. The request was made by Senate Minority Leader Robert J. Dole (R-Kan.) and Sen. Strom Thurmond (R-S.C.), ranking Republican on the Judiciary Committee, in a meeting with Majority Leader Robert C. Byrd (D-W.Va.) and Biden.

Mark Goodin, an aide to Thurmond, said Biden promised an answer after consulting with other Democrats on the committee. He quoted Biden as saying the Democrats had "no interest in stalling" the nomination process.

Earlier yesterday, Biden defended the decision to begin hearings on the Bork nomination on Sept. 15 after Sen. Gordon J. Humphrey (R-S.C.) urged an earlier start. He said hearings on Supreme Court nominations normally begin 45 to 60 days after they are formally submitted to the Senate.

Biden also dismissed criticism that the Supreme Court is likely to begin its next term Oct. 5 with only eight justices. He said there have been "numerous occasions" in the past when the court met without a full complement of nine justices.