A weary Judge Robert H. Bork, completing his fourth day of testimony before the Senate Judiciary Committee, insisted yesterday that he has "no ideological agenda" and no intention of trying to sweep aside established precedents if he is confirmed as a Supreme Court justice.

Under fierce attack by his liberal opponents, President Reagan's choice to fill the seat of retired justice Lewis F. Powell Jr. sought to assure the sharply divided committee that it can rely on his testimony this week and that he has not tried to conceal his objectives in order to win Senate confirmation.

"It would really be preposterous for me to sit here and say the things I have and then go on the court and do the opposite," he said. "I would be disgraced in history."

Later, Bork told the committee, "I also took an oath to tell the truth and I take an oath very seriously. I did tell the truth."

Bork's assurances did nothing to stem the assault by his most vocal critics. Sen. Edward M. Kennedy (D-Mass.) played a tape recording of Bork saying two years ago that he did not think precedent "is all that important" and charged that Bork is "a walking constitutional amendment" who "again and again has suggested he is ready to turn back the clock" on many issues.

"You are not a frightening man, but you are a man with frightening views," Sen. Howard M. Metzenbaum (D-Ohio) said after attacking a ruling Bork authored upholding a chemical company's decision to offer some of its female employes a choice between being sterilized or losing their jobs.

Bork's Republican defenders assailed what Sen. Alan K. Simpson (R-Wyo.) called the "lies" his opponents were attempting to spread.

Shortly after 8 p.m. last night, the Judiciary Committee abandoned its hope of completing its questioning of Bork and scheduled another three hours of testimony starting at noon today.

As Bork's extraordinary testimony on legal, political and philosophical issues neared its end, it remained unclear whether he was any closer to winning endorsement from the committee and eventually confirmation from the full Senate. But Bork, who retracted some of his controversial conservative views during the hearings and forcefully reiterated others, appeared to have damaged his standing with two of the three Judiciary Committee members who are thought to be undecided.

One of them, Sen. Dennis DeConcini (D-Ariz.), said, "It's still possible I could vote for him." But, describing himself as "troubled" by some of the shifts in longstanding views Bork voiced in his testimony, DeConcini said: "The predictability or nonpredictability of Robert Bork is the biggest single question I have when you put it all together."

Another key swing vote, Sen. Arlen Specter (R-Pa.), continued his sharp and skeptical questioning of Bork yesterday, and said he would continue for another 90 minutes today.

The issue of Bork's personal credibility continued to dominate the hearings as his critics charged that some of the views he expressed this week were at sharp and questionable variance with longstanding positions Bork has espoused as a Yale Law School professor and, since 1982, as a judge on the U.S. Court of Appeals here.

Much of yesterday's hearing centered on Bork's views on the importance of Supreme Court precedents. Bork has a prolific record of often stinging criticism of several key high court decisions that his opponents charge he is eager to overturn.

Bork, however, has testified repeatedly that many of these decisions are now firmly rooted in "settled law" and established customs, and that even if he still disagreed with them he would make no attempt to reverse them.

In his opening statement, Bork told the committee "a judge must give great respect to precedent" and that "it is one thing as a legal theorist to criticize the reasoning of a prior decision" and "another and more serious thing altogether for a judge to ignore or overturn a prior decision."

Bork testified yesterday that "judges respect precedent in all cases, somewhat less in constitutional matters" than when dealing with laws enacted by legislative bodies. Many of the Supreme Court's most controversial decisions on First Amendment rights and the Constitution's equal protection guarantees are now so well established that "it is simply too late for any judge to try to tear them up," he said.

Bork's critics countered yesterday by quoting statements suggesting he took a less serious view of the importance of precedent. Attempting to dramatize the dispute, Kennedy played a tape recording of Bork answering a question at Canisius College in Buffalo, N.Y., in October 1985.

Bork's rich, baritone voice on the tape echoed through the Senate Caucus Room as he responded to a query on "what do you do about precedent."

"I don't think that in the field of constitutional law precedent is all that important," he said. The reason, Bork continued, is that if the Supreme Court miscontrues the Constitution there is no recourse from the decision.

"You {the high court} are the final word," he said. "And if you become convinced that a prior court has misread the Constitution, I think it's your duty to go back and correct it . . . . I don't think precedent is all that important."

After the recording was played, Bork reaffirmed that "generally what I said is correct." But he objected that the statement was made "in a give-and-take, question-and-answer session after a speech" when, for the only time, he neglected to mention the importance of "settled law."

"Your own words cast strong doubt on your adherence to precedents you disagree with," Kennedy replied.

Sen. Howell Heflin (D-Ala.), another undecided vote on the committee, told Bork that some of his writings and speeches "suggest an agenda that is somewhat contrary" to his assurances about the importance of precedent. Heflin also asked Bork to respond to assertions that "you could do terrible harm to the rights of minorities and the racial progress that has been made."

"That assumes there are four other judges {on the Supreme Court} who have sinister views, which is not true, and it ignores my record as a judge," Bork replied.

Senate Majority Leader Robert C. Byrd (D-W.Va.) said he was as undecided as DeConcini, Heflin and Specter. He questioned Bork closely on his view that members of Congress should have no legal standing to bring suit against members of the other branches of government.

"You're saying to members of Congress, 'You ain't never going to get into this court,' " Byrd said.

Metzenbaum zeroed in on an emotion-laden issue involving the American Cyanamid Co. Writing in 1984 for a unanimous three-judge appeals court panel including Antonin Scalia, now a Supreme Court justice, Bork upheld an administrative law judge's ruling that the company had the right to offer female employes of child-bearing age a choice between sterilization and dismissal.

Bork said the company could not find a way of reducing the level of lead in one of its production departments below the point where it no longer posed a threat to an unborn fetus. He said that rather than fire the women or move them to lower-paying jobs elsewhere in the plant, American Cyanamid offered the sterilization option and suggested that some of the women were probably "glad to have the choice."

"That is not a pro-sterilization opinion," Bork said. "It is not an anti-women opinion."

"Judge," Metzenbaum said, "I must tell you it is such a shocking decision. I don't understand how you as a jurist could put women to a choice to be fired or be sterilized."

Metzenbaum continued: "You say ignore your academic writings; they are merely speculative. You say look at your record on the court, it's much more reliable.

"I cannot tell you strongly enough that the women of this country are terribly, terribly apprehensive about your appointment . . . . The women's groups are afraid. The fact is, Judge Bork, they do fear you -- blacks as well."

Bork replied, "I can't say this enough times. I supported black equality. I have never said or decided anything that should be frightening to women."

Metzenbaum returned to the hearing later yesterday with a telegram he said he received from Betty J. Riggs of Parrisville, W.Va., site of the American Cyanamid plant. In it, she said "only a judge who knows nothing about women" could believe some welcomed the choice.

"I was only 26 years old but I had to work so I had no choice," Riggs said in the telegram, adding, "This was the most awful thing that happened to me."

Simpson said last night that Republican committee staff investigators had determined that Riggs was asked to send the telegram by her lawyer, Joan Bertin, who composed the text.

"I think that's offensive conduct for a lawyer," Simpson said.

As the hearing dragged on through the day, the toll from the constant pounding he has undergone showed on Bork's face. Asked by Simpson how he felt about the confirmation process, the bleary-eyed jurist said:

"I've not yet had time to gather my thoughts. Let me say, it's not terribly enjoyable."