MIAMI, DEC. 1 -- Tapes of telephone conversations of deposed Panamanian strongman Manuel Antonio Noriega, a compulsive caller who often spends up to eight hours a day on the phone from jail, have long provided federal agents with investigative leads to bolster what they say is now a formidable drug and racketeering case against him.

So talkative is Noriega that officials monitoring his calls to places such as Hong Kong and Spain, as well as to Panama City, long ago gave up any effort to transcribe all of them. His dismayed defense lawyer, Frank A. Rubino, says he warned his client he was making the calls "at his peril."

"You can lead a horse to water," Rubino said, "but you can't make him drink."

The taping at Miami's Metropolitan Correctional Center first came to light when Cable News Network last month obtained snippets of Noriega's conversations. In a legal controversy that went all the way to the Supreme Court, Noriega's defense team argued that privileged telephone contacts between them and their client had been made available to prosecutors, a charge that is still under investigation along with the question of how CNN obtained the tapes.

But sources here said that the uproar over CNN's scoop obscured the magnitude of the continuous taping of Noriega's calls. Excerpts of the tapes have been made available regularly to the government under a subpoena granted after Noriega's arrest 11 months ago. The sources maintain investigators have had no access to privileged attorney-client calls, but have found those conversations to which they are legally entitled to be somewhat helpful in assembling the case now scheduled to go to trial on Jan. 28.

At the same time, however, they describe the telephone leads as a relatively minor part of what has been an all-out government push to use every available means to convict the former "Maximum Leader" of the Panamanian people.

Sources familiar with the investigation and a growing court record say that as a result of these efforts, the government now has a far broader array of witnesses than when Noriega was first charged who will flesh out the central allegations that he headed a lucrative enterprise that provided safe haven for Colombia's Medellin drug cartel.

The prosecution still faces major obstacles, including repeated defense allegations of government misconduct and the potentially explosive information contained in classified documents about Noriega's work as a paid U.S. intelligence agent. And, despite the progress, the government's case still rests largely on the testimony of convicted criminals.

The tapes of Noriega's jailhouse conversations have prompted investigators to pursue several of his associates in Panama. The casual conversations of at least one other codefendant at the same Miami facility also have drawn official attention. In a court filing prosecutors claimed that codefendant William Saldarriaga "confessed to another cell mate" his involvement in a drug shipment and claimed "Noriega was behind the entire deal." According to Saldarriaga's lawyer, "he never said that."

Additionally, government agents in Panama have examined several rooms full of documents in a Panama City warehouse that were among Noriega's possessions seized after the Dec. 20, 1989, U.S. invasion that toppled him. While failing to provide the "smoking gun" that they had hoped would directly tie Noriega to drug shipments, investigators have found a mixed bag of potentially useful information, including flight logs of Noriega's jet, as well as some titillating tidbits such as a letter from Noriega's doctor attesting that he does not have AIDS.

The larger, and more successful, effort has been to line up other witnesses. In the 11 months since Noriega was brought to Miami, an expanded cast of potential witnesses has been assembled that will include former Panamanian military officers who served under Noriega, business associates, close confidants, drug dealers and employees of the Medellin cartel.

One government official observed that these new witnesses together can weave a mosaic that clearly features Noriega as the center of an illicit drug racketeering operation.

The original indictment charging Noriega with accepting $4.6 million in payoffs from the Colombian Medellin drug cartel was based largely on the testimony of Floyd Carlton Caceres, who said he transported drugs for Noriega as his personal pilot.

Richard Gregorie, the prosecutor who wrote the 1988 indictment and is now in private practice in Miami, observed that Carlton remains "the centerpiece" of the government's case.

"All of these {other} guys can corroborate pieces of Carlton's testimony," he said.

A special team of Drug Enforcement Administration agents is assigned full time to the case, and federal prosecutors have spent months in Panama and elsewhere tracking down witnesses who have any knowledge of the cartel's operations or Noriega's activities.

"They're visiting prisons all over the world and offering to let them out if they'll give a little kernel of fact about Noriega," said Miami defense lawyer, Samuel Burstyn. "It's the hottest 'Get Out Of Jail Free' card around."

Burstyn said his client, Noriega associate Lt. Col. Luis del Cid, who is charged with acting as liaison, courier and emissary in Noriega's transactions with drug traffickers, is on the verge of cutting a "very appealing" deal with prosecutors in exchange for testimony against his former boss.

The lawyer declined to detail how del Cid could assist the prosecution, but said del Cid was Noriega's "very well-trusted confidant." The government asserts that del Cid accepted drug payoffs on Noriega's behalf. The pilot, Carlton, claims he delivered a payoff of $200,000 in U.S. currency to del Cid intended for the Panamanian leader.

In addition to del Cid, sources said, critical testimony will come from Boris Olarte, a former employee of the cartel who is expected to say that he twice delivered drug payoffs -- $250,000 the first time and approximately $4 million a few months later -- to Noriega for the protection of cocaine shipments through Panama.

"He brought this to Noriega's home," said Gregorie, who questioned Olarte in 1988.

Enrique Pretelt, a wealthy Panamanian jeweler who was Noriega's business partner in several ventures, also has agreed to testify. Pretelt, 47, has pleaded guilty in a separate case to conspiring with Noriega to launder drug profits and import 400,000 pounds of marijuana.

"He will be an excellent witness for the government," said his attorney, George Tragos. ". . . He was one of his {Noriega's} best friends, and he went with him a lot of places."

Eduardo Pardo, a longtime professional pilot originally charged with Noriega, also will testify in support of Carlton's allegations.

"He flew General Noriega and his family," said William Meadows, Pardo's attorney. Pardo originally was charged with ferrying $800,000 in drug proceeds from Fort Lauderdale, Fla., to Panama; he pleaded guilty and is serving a prison sentence.

Alfredo Sanchez, a former Defense Intelligence Agency operative from Panama, also has pleaded guilty to drug charges and currently is a protected government witness. A federal prosecutor asserted at Sanchez's 1988 sentencing that Sanchez "will allow us to explain a great deal of the conspiracy, which was sort of a blank spot in the Noriega case."

As a result of these and other efforts, informed sources say prosecutors now are constructing a far more elaborate case against Noriega than that outlined in the original 30-page indictment against him.

Noriega defense attorney Rubino, not surprisingly, has taken a dim view of the government's zeal. Last week, he complained to the federal court that the government had "engaged in misconduct heretofore unimaginable." He said that he was approached in September by a government witness who offered not to testify against Noriega in exchange for a bribe.

"We now believe that this was a setup designed to entrap defense counsel into committing a crime," Rubino said in a motion to dismiss the charges against Noriega. The incident is under investigation by the court.

Much of the extensive pretrial courtroom wrangling between lawyers that has marked the case so far has been over side issues -- like how the defense team is going to be paid since the government arranged for the freezing of approximately $20 million allegedly stashed by Noriega in 27 foreign bank accounts.

So public have been these arguments over seemingly tangential issues that presiding U.S. District Judge William M. Hoeveler last week worried from the bench about the perception that Noriega will not get a fair trial. Hoeveler even allowed Noriega, in his last court appearance Nov. 16, to give a dramatic 18-minute speech expressing his outrage about his ability to get a fair trial.

"They have taken my money, deprived me of my lawyers, videotaped me in my cell, wiretapped my telephone calls with my lawyers and even given them to the {Guillermo} Endara government {in Panama} and to the press," Noriega said. "The battle I face ahead is very similar to when the United States invaded my country. That was one-sided and unfair, and so is this battle."

Opinions vary on just how much the government has been able to strengthen its case since the invasion and arrest. Attorney Joel Rosenthal, who represents Noriega codefendent Amet Parades, characterized the government's case against Noriega as "an overwhelmingly strong one." But del Cid attorney Burstyn said that despite the assistance his client is prepared to provide, he knew of no witnesses who could link Noriega directly to drug transactions. Neil Taylor, another defense attorney, pointed out that prosecutors face serious challenges to the credibility of their witnesses.

"The people making the allegations are highly questionable," he said.

Even Gregorie, the former prosecutor, conceded that if the government has an Achilles heel, it is that prosecutors are relying heavily on testimony from convicted drug dealers.

Some of the best opportunities for the defense may lie in the 50 boxes of documents seized in Panama. The documents reflect Noriega's extensive cooperation with the DEA in various drug enforcement operations; his help in seizing drugs and apprehending suspects and his cooperation in the destruction of marijuana fields. They also are likely to bolster his expected claim that he was authorized by U.S. officials to engage in activites now being portrayed as illegal.

"It appears to me the documents cut both ways in this case," said Rosenthal.

The chaotic circumstances during which many of the incriminating documents were seized after the invasion make some of the documents -- which might be helpful to the government -- virtually unusable as evidence in court, according to one official source.

But government agents said they believe some items will be helpful. For example, last Jan. 8, DEA agent John Powell, accompanied by members of the Army's 470th Military Intelligence Unit, found Noriega's Lear jet parked outside a burned out hanger at the Punta Paitilla military airport in Panama City.

Inside the hangar, in a small map room, Powell found 17 computer disks, along with the flight records of Noriega's jet. Though the disks were damaged by heat, the FBI was able to extract much of the data, which agents hope will offer a road map to Noriega's travels.

Other documents the government hopes will bolster the credibility of its witnesses include: the flight logs of pilot Pardo; records from the Bank of Credit and Commerce International, which was used extensively by Noriega; and records from Pretelt, Noriega's former business partner.

Separate documents relating to Noriega are held by various U.S. agencies that relied upon him as a key intelligence operative in Central America. Officials assume Noriega will argue that many of his actions were taken at the behest of U.S. intelligence officials.

Rubino has subpoenaed officials such as CIA Director William H. Webster and Joint Chiefs Chairman Gen. Colin L. Powell, and investigators say they anticipate Noriega will try to embarrass the government on such subjects as Iran-contra.

"It is not going to be pretty," said one senior official familiar with the investigation. "There will be enough embarrassment to go around."

Rubino has complained about the government's unwillingness to be forthcoming with potential evidence included in these documents, and on one occasion Judge Hoeveler has agreed. When Rubino protested the government's offer of a two-page summary of 600 classified documents, for example, Hoeveler ordered the release of all 600 pages.

Rubino said he is handicapped by the sheer size of the team the government has been able to deploy to work the case. While large squads of DEA agents and federal prosecutors have swept up every shred of new evidence in Panama, Rubino said he has done relatively little investigation on Noriega's behalf because he has not been paid.

"We have no investigation done because we have no money," Rubino said. "Factually, we're 11 months behind on this case."