In trying to break Gen. Manuel Antonio Noriega's grip as military strongman of Panama, the Reagan administration frequently has seemed to practice a sleek, 1980s' version of an old-fashioned coup d'etat -- toppling a government not with raw military power but through relentless diplomatic, economic and legal pressures.

Administration moves have ranged from calls by President Reagan and Secretary of State George P. Shultz for Noriega to step aside and permit a return to civilian democracy, through a cutoff of U.S. economic and military aid, to the virtually unprecedented indictments of Noriega on drug trafficking charges by two federal grand juries in Florida earlier this month.

On Thursday came another step when figurehead civilian president Eric Arturo Delvalle turned against Noriega, who had put Delvalle in office. Delvalle's unsuccessful attempt to fire Noriega occurred only a week after he met secretly in Miami with Elliott Abrams, assistant secretary of state for inter-American affairs, to discuss possible inducements for Noriega to leave Panama.

"If we wanted to build up the Reagan administration's reputation as a skillful practitioner of power politics, Panama would seem an almost made-to-order target," a senior State Department official acknowledged.

"It's a tiny country of major national security importance because of the canal, with a corrupt military dictator disliked on all sides of the political spectrum in Washington. If we encouraged the idea that we're running a carefully conceived destabilization campaign, we'd be applauded all around for striking a blow for democracy and against the cocaine traffickers."

But, he added, "only one thing prevents us from taking credit -- it didn't happen that way. {While} we've had a clear policy of favoring an end to Noriega's control {since unrest last summer} . . . everything we've done has been a consequence of what's happened down there. We have reacted to events, we didn't create events."

Numerous U.S. diplomatic, military, intelligence and law enforcement officials made the same point in recent interviews. All agreed that the large number of federal agencies with competing interests in Panama often resulted in a somewhat schizophrenic decision process.

Prior to last summer's anti-Noriega unrest, they said, the administration, influenced largely by the Pentagon, Central Intelligence Agency and Drug Enforcement Administration, regarded Noriega as a strategic intelligence asset. When, as one source put it, "it was decided to officially reclassify him as a bad guy," many old differences remained unresolved, sending confusing signals about U.S. intentions.

Knowledgeable officials insist that the federal drug indictments of Noriega were not a carefully calibrated administration step. Instead, they said, the U.S. attorney's office in Miami pressed the probe and kept the State Department and even DEA at arms length.

This is a sore point with the DEA, which long insisted there was no credible evidence of Noriega's drug involvement, and praised him publicly as an ally in the U.S. narcotics fight. DEA officials still privately call the indictments an ill-advised "publicity stunt" that offer no hope of convicting Noriega even if he ever is in a U.S. District Court and that have damaged the drug war by cutting off Panama's allegedly valuable cooperation.

State Department officials say the indictments make more difficult any face-saving arrangements for Noriega to step aside. Despite denials, Delvalle met Abrams to discuss possibly dropping the indictments as part of a deal. But disclosure of the talks provoked outrage in Congress and elsewhere, forcing an administration retreat from any deal.

From a 1968 military coup until his death in a 1981 plane crash, Gen. Omar Torrijos ruled Panama, becoming legendary for negotiating the 1977 treaties with the United States to bring the canal under Panamanian control at the end of the century.

Noriega, a Torrijos lieutenant and military intelligence chief, took control by 1983. He cemented ties with officers in Panama and Central America and U.S. intelligence officials, who at first regarded him as "an asset."

But, administration officials say, reports soon came that Noriega was expanding the military's traditional graft into narcotics. Some reported he was a partner of the notorious Medellin cartel, the ruthless, Colombia-based cocaine ring then spreading throughout the Caribbean into the United States.

Initially, they said, little was done because concerns with Central America were focused on Reagan's top priority of combatting Nicaragua's Marxist Sandinista government by support of the contra insurgents. Indeed, the administration has denied allegations that the United States winked at Noriega's activities because he trained contras in Panama.

Several officials said discussions about Panama usually were resolved in favor of what one called "the Nestor Sanchez faction." Sanchez, a former CIA official and deputy assistant secretary of defense important to Central America policy in the 1980s, was a friend of Noriega. He is said to have argued in policy meetings that Noriega was providing important intelligence and was Washington's best hope for ensuring the safety of the canal by maintaining stability in Panama.

The sources said U.S. thinking about Noriega began changing in mid-1985 when Abrams became the State Department's Latin American policy chief. Since the Iran-contra hearings with their revelations that Abrams gave misleading testimony to Congress, he has been seen primarily as an ideologically intense opponent of Nicaragua.

But he also has taken a tough stance against rightist dictatorships, such as Chile and Paraguay. In the fall of 1985, he turned his attention to Noriega after Hugo Spadafora, a Noriega critic, was decapitated under circumstances implicating the Panamanian military.

Abrams became an outspoken advocate of prodding Noriega over his corruption and human rights records. In December 1985, shortly after becoming national security adviser, John M. Poindexter made a secret trip to Central America that sources said included giving that message to Noriega.

At the time, Noriega told fellow officers that Poindexter had reaffirmed U.S. backing for him. But after his recent drug indictment, he charged that Poindexter had demanded at the meeting that Panama become a "beachhead" against Nicaragua.

Meanwhile, an unusual congressional coalition formed against Noriega, ranging from conservatives such as Sen. Jesse Helms (R-N.C.) to liberals such as Massachusetts' two Democratic senators, Edward M. Kennedy and John F. Kerry.

But last June, events took a dramatic turn when Col. Roberto Diaz Herrera, a former deputy military commander, publicly charged Noriega with responsibility for the Spadafora murder and other crimes, including using Panamanian banks to launder drug money. The charges ignited the continuing unrest.

On June 30, the administration, in a speech by Abrams, declared it was time for democracy to return.

In December, Richard L. Armitage, an assistant secretary of defense, met secretly in Panama with Noriega. While most officials insist he "delivered the message," some say the Pentagon was reluctant to get into a confrontation with Noriega and that Armitage used language that Abrams and others at the State Department regarded as disappointingly soft.

"The real problem was not that Armitage pulled his punches but that too much time was spent arguing about whether to send a messenger, who the messenger should be and what he should say," one official said. "The idea of the trip {came} when Noriega seemed to be embattled. But by the time Armitage went, several weeks had passed, the situation had changed and the whole thing was a bit of an irrelevant misfire."

Then, at the end of October, Panamanian exiles here advised State Department officials to talk with Jose I. Blandon, a Noriega political hanger-on sent to New York as Panamanian consul general.

Blandon said he was authorized by Noriega to work out a settlement. But talks were inconclusive, and ended abruptly with Blandon branded a traitor by Noriega and fleeing to the United States at year's end.

Blandon now became a highly publicized figure telling of Noreiga's corruption to the media, Congress, and the grand jury in Miami.

"That was a major turning point," a State Department official said. "As recently as early January, we were told by the Justice Department that there was no likelihood of their investigations leading to any indictments in the forseeable future."