In the last weeks of his presidency, Richard M. Nixon tried unsuccessfully to halt the prosecution of his friend and former Cabinet official, John B. Connally.

According to eight sources familiar with the events, Nixon sought to quash the government's plea-bargaining agreement with the crucial witness against Connally and to fire the assistant attorney general who was responsible for the agreement.

The Nixon intervention was halted when Deputy Attorney General Laurence Siberman threatened to resign and when Attorney General William Saxbe said the president would have to fire him first.

"Tell the White House to piss up a rope," Saxbe is reported to have said at the time.

Connally, now a Republican candidate for the presidency, was under investigation at the time for allegedly accepting an illegal $10,000 gratuity from an association of milk producers in return for his efforts as treasury secretary to boost federal price supports for milk. Subsequently, he was tried before a jury in U.S. District Court here and was acquitted of the charges.

Nixon's unusual action occurred on April 30, 1974, the same day he released edited transcripts of the White House tapes to the House Judiciary Committee. At that time, Connally had returned to private law practice in Houston.

Nixon telephoned Silberman and ordered him to revive a series of fraud charges against Jake Jacobsen, the principal witness against Connally. Since Justice, in a plea-bargaining, arrangement, had agreed to drop the fraud charges against Jacobsen in exchange for his testimony against Connally, Nixon's action in effect would have scuttled the plea-bargaining agreement.

The president also told Silberman that Assistant Attorney General Henry Petersen, who had approved the plea-bargaining arrangement with Jacobsen, should be fired.

There is no evidence that Connally asked Nixon to intervene at Justice. Connally says he cannot recall ever even discussing his case with Nixon, Nixon would not respond to requests for comment.

Asked in a telephone interview last night about Nixon's call to Silberman, Connally said, "I know nothing about it. I doubt that he (Nixon) did it. It's news to me if it happened. I never discussed the plea bargaining or my case with him. I didn't ask anything of him, and as far as I know he didn't follow (the case)."

According to sources close to Silberman, he immediately prepared a seven-page "memo to the file" describing the events. He did this, sources say, because he was concerned that the president's call may have been part of a conspiracy to obstruct justice.

Silberman, however, refuses to comment on whether he thought the actions constituted a possible conspiracy.

The sources say that Silberman then forwarded the memo to the Watergate special prosecutor. But the prosecutor's office contends that it did not receive the memo until five months later. No one was able to explain why the memo took five months to be delivered.

The government charged that the $10,000 had been delivered to Connally by Jacobsen, then an attorney for the Texas-based milk producers cooperative. bA onetime White House aide to Lyndon B. Johnson, Jacobsen had been a close personal and political friend of Connally.

At the time of the federal milk probe, Jacobsen already was under indictment in Abilene, Tex., in another case, for allegedly lying to a federal grand jury and for allegedly misapplying bank funds. Under the plea-bargaining agreement with the Watergate special prosecutor, the Texas charges were to be dropped in exchange for Jacobsen's testimony in the Connally trial.

A detailed account of the abortive Intervention by Nixon in the Connally case was pieced together from interviews with eight sources familiar with the events. Among those who witnessed these events were three sides to Silberman, Silberman, who is now an executive with Crocker National Bank in San Francisco, confirmed the account provided by the other sources.

Saxbe also confirmed the substance and quotations from his conversation with Silberman.

Several of the sources read the "memo to the file" Silberman had prepared and forwarded to Deputy Special Prosecutor Henry S. Ruth, who was in charge of the milk fund investigation.

April 30, 1974, was a tense day at the embattled Nixon White House.

Presidential aide, Alexander M. Haig was anticipating a severe reaction to the president's decision to send the House Judiciary Committee only heavily edited tape transcripts instead of the White House tapes. Haig telephoned Attorney General Saxbe seeking assurance that he would support the president. Haig was also troubled by a call from the special prosecutor for a grand jury probe of the 18 1/2 minute gap in one of the tapes.

Saxbe was out of twon, so telephone calls that morning were passed to Silberman. No sooner had he hung up from the Haig call than presidential lawyer James D. St. Clair called to argue similar prints. But in the middle of the St. Clair exchange, on aide passed Silberman a note indicating that Nixon was holding on the line.

At 11:57 a.m., the president began the conversation in a friendly, chatty manner. "Larry, are you picking good judges over there?"

As deputy attorney general, Silberman was responsible for proposing nominees to fill federal judicial vacancles.

"Yes, Mr. President, insofar as we have the discretion," Silberman responded. He had never before received a call from the president.

"You know what I mean about good judges?" the president asked.

Silberman said he was sure he meant men like Felix Frankfurter, who believed in judicial self-restraint.

"That's exactly right," Nixon said.

Nixon then turned the conversation to the Connally case.

He complained that someone in the Justice Department was making arrangements to drop federal felony charges pending against Jacobsen in Texas in return for his testimony against Connally. That was an abuse of the plea-bargaining process, Nixon said, because Jacobsen's testimony against Connally was being brought by letting him off on the more serious felony charges and allowing him to plead guilty to a misdemeanor.

Silberman reminded the president that the Connally case was being prosecuted not by the Justice Department but by the Watergate special prosecution force. That force, Silberman told the president, had been guaranteed complete freedom from interference.

Nixon responded that the charges against Jacobsen, which were being dropped, had been brought originally in Abiline by a local U.S. attorney. That attorney was under the jurisdiction of the Justice Department, Nixon said.

Silberman told, Nixon that he was unaware of the details of the plea bargaining with Jacobsen, but he said he would look into the matter. Nixon asked him to do that and to call him within an hour.

Silberman immediately called Assistant Attorney General Petersen, who was meeting with his staff at a planning seminar at the Airlie House conference center near Warrenton, Va.

Petersen explained to Silberman that it was customary to drop charges in one jurisdiction in exchange for a guilty, plea and cooperation in another jurisdiction. In the milk case, Jacobsen had agreed to plead guilty to a felony -- not to a misdeameanor, as Nixon had asserted -- of paying the illegal $10,000 gratuity to Conally.

At 12:55 p.m., Silberman called the president. He relayed Petersen's position that there was nothing improper or unusual about the plea bargain with Jacobsen.

The president grew agitated, according to the Silberman "memo to the file." Repeatedly interrupting Silberman, Nixon argued heatedly that the plea bargain was nothing more than a plot to get Connally by inducing Jacobsen to testify against him.

When Silberman tried to explain to Nixon that the matter was being handled normally, Nixon countered: "I want it straight. I don't want any dancing around."

Then the president's voice rose. "I don't want to hear about normal procedures. I want orders (to reinstate the charges against Jacobsen)."

Told that Petersen would not reinstate the Texas charges against Jacobsen Nixon replied: "Well, Henry Petersen will just have to go."

Nixon concluded the exchange by telling Silberman, "Call Haig back in one hour," and he hung up.

Silberman consulted briefly with his aides and decided that if, in fact, the president insisted on ordering the reinstatement of the charges and the firing of Petersen, Silberman would have to resign. Figuring that Saxbe would be faced with the same prospect, he asked the FBI to call the agent traveling with the attorney general.

That morning, Saxbe had been at Newsweek magazine for an interview with the editors. Then he had gone to a private club on Shelter Island with Time Inc., President James Shepley for a pheasant shoot.

At 1:07 p.m., Silberman reached Saxbe.Recalling that day, Saxbe, now an attorney in Mechanicsville, Ohio, and currently state chairman of George Bush's presidential campaign, says he argued against anyone resigning. g

"I told Silberman. 'You're out of your mind. I'm not going to resign and neither should you. They can fire us if they want.'" Saxbe now says he wasn't aware that the call to Silberman had come directly from the president. He concluded his conversation with Silberman by saying: "Tell the White House to piss up a rope. And don't bother me again; the hunting is good."

Asked if the "rope" expression is a favorite of his, Saxbe said, "No. But it seemed appropriate at the time."

After Saxbe hung up, Silberman called Haig, who said he didn't know anythiing about the Nixon call. Silberman told him that he and Saxbe would not comply with the president's instructions. Haig said he would get back to Silberman.

Several hours later, Haig called and said: "Just forget the whole matter."

When asked recently about the episode, Haig said he did not recall if the president called Silberman. However, he said that, if the April 30 event happened Haig was sure he would have told Silberman, "You do what's right."

Connally said during an interview last month that he does not recall ever discussing either his case or the Jacobsen plea bargain with Nixon. Additional inquiries about the Nixon call to Silberman drew no response from either the former president or Connally.

Nixon's private logs of presidential meetings show that he met with Connally on April 19 for 90 minutes -- the longest meeting with a non-White House aide during that period.

Connally said last night that he did not recall the purpose or subject of his April 19 meeting with Nixon.

The logs are blank for the day of April 30, although Haig and others recall that Nixon did have meetings on that day.

One knowledgeable former presidential aide says that at about this time Nixon ordered that informal meetings with aides and intimates no longer be recorded in the logs.

Two sources said that Silberman wrote his "memo to the file" after the final conversation with Haig, and they recalled that he immediately forwarded a copy to Ruth, the deputy special prosecutor. But two sources who were with Ruth's office at the time say that the memo did not arrive until the following fall -- after Nixon had resigned and been pardoned by President Gerald R. Ford.