PANAMA CITY -- As Panama's antigovernment protest movement enters its third month, it is becoming increasingly clear that it will take more than street demonstrations and business strikes to oust the country's military strongman, Gen. Manuel Antonio Noriega.

Opposition leaders and foreign analysts agree that getting rid of the 49-year-old general, who has ruled Panama behind the scenes since 1983, is likely to require a move from within Noriega's 15,000-member Panamanian Defense Forces.

Noriega's opponents express hope that an internal military split, which they view as necessary to produce such a move, is already developing. But foreign analysts say there is no sign of any crack in the Defense Forces' loyalty to Noriega, who holds the title of commander in chief and ranks as Panama's only serving general.

If an internal break were to develop, some analysts say, it would probably come from lower-ranking officers -- from major on down -- who are thought to be more oriented toward military professionalism and less tainted by the alleged large-scale corruption associated with the military hierarchy.

However, it is generally agreed that much more intensive protest activities and a considerably greater deterioration of social and economic conditions would have to evolve to bring about such a break. In fact, Noriega so far seems to be weathering the storm of protest.

"It's going to be a long haul," said one foreign analyst. "Noriega is not going to leave until the {military leadership} decides he should go." For that to happen, the analyst added, "the economy would really have to go to hell in a handbasket, and while it's a slippery slope, things haven't gotten that bad yet economically."

If the major popular upheavals of the past decade are any indication, rifts in military unity can develop suddenly as the result of prolonged popular protests.

In Iran, a protest movement against Shah Mohammad Reza Pahlavi went on for more than a year -- marked by massive street demonstrations, the imposition of martial law, widespread rioting and clashes between protesters and troops. Then, on Feb. 1, 1979, Ayatollah Ruhollah Khomeini returned from exile to Tehran. Ten days later, Air Force cadets mutinied at a Tehran military base, and by that evening the shah's once-mighty armed forces had crumbled and 2,500 years of Persian monarchy had been overthrown.

In the Philippines, the assassination of opposition leader Benigno Aquino in August 1983 launched a protest movement against President Ferdinand Marcos that dragged on for nearly three years. Then, on Feb. 22, 1986, the Philippine defense minister, the Armed Forces chief of staff and about 300 troops suddenly revolted and barricaded themselves inside Manila's Defense Ministry compound. Three days later, military support for the government had collapsed, Marcos had fled the country and Corazon Aquino, the widow of the slain politician, had taken over as president.

In Panama, military power rests with the Defense Forces' 19-member General Staff, made up of colonels and lieutenant colonels loyal to Noriega. It is a "collegial" body that reaches decisions as a group and allegedly shares the wealth generated by military-owned enterprises, such as explosives manufacturing, and various corrupt practices, Panamanian critics and foreign analysts say.

"It's not a one-man band here at all," one political analyst said.

So far, two incidents have generated questions about sentiments within the tightly knit Defense Forces. In early June, allegations by Noriega's former second-in-command, retired colonel Roberto Diaz Herrera, about military corruption and about Noriega's involvement in murder and election fraud not only triggered the current wave of popular protests, but also stirred speculation on whether serving officers shared his views.

Then, on July 24, Noriega's predecessor, retired general Ruben Dario Paredes, publicly blamed Noriega for the current unrest and urged him to resign to spare the country "greater violence, destruction and bloodshed." Paredes' views were aired in a television interview and in an open letter published in the opposition newspaper, La Prensa.

Within three days, the military had shut down La Prensa and two other opposition papers, imposed de facto censorship on radio and television news programs and raided the house of Diaz Herrera, arresting him and 45 followers.

Some opposition and foreign analysts suggested that while Diaz Herrera and his repeated allegations were a thorn in Noriega's side, the statements of Paredes and the prospect that they might find resonance in the military presented Noriega with a more serious potential problem. Thus, the press crackdown and the raid on Diaz Herrera's house might have been intended to send a message to active-duty officers that dissent would not be tolerated, the analysts said.

"Paredes has people who were or are beholden to him in the military," said political opposition leader Ricardo Arias Calderon, head of the Christian Democratic Party. "There could be an allegiance drainage. A significant number of officers in the mid and upper ranks and a significant number of troops are already asking, 'Where is this man {Noriega} leading us?' "

Other opposition sources close to Arias Calderon acknowledge that neither his party nor other opposition groups have any mother lode of information about military dissent, because the Defense Forces' G2 intelligence section, formerly headed by Noriega, closely monitors and restricts officers' contacts with the opposition. Readings of dissent appear to be based largely on speculation that some majors may be getting impatient with the reluctance of a few colonels in the General Staff -- as well as of Noriega -- to retire after 25 years of service in accordance with Panamanian military tradition. This reluctance has created a bottleneck that impedes lower-ranking officers from moving up.

Military and civilian government spokesmen declined to discuss Paredes' appeal and deny the existence of any anti-Noriega feeling in the military. But Noriega-controlled publications have virulently attacked Paredes recently, calling him "the worst commander that the Defense Forces have ever had."

The United States, for its part, has made it clear that it opposes Noriega and wants an "apolitical" military. Despite the evident U.S. distaste for the strongman and the recent suspension of American aid to Panama, however, the U.S. Army is obliged to continue working with the Panamanian Defense Forces under terms of the 1977 Panama Canal Treaties.

One purpose of the anti-Noriega demonstrations and strikes is to show the extent of opposition to Noriega and -- the opposition hopes -- to weaken support for him within the military, opposition sources say.

But Noriega responded to a successful two-day general strike last week by staging daily demonstrations of his own, including motorcades, street parties and a massive turnout Friday for an annual ceremony commemorating the anniversary of the death of popular Panamanian leader general Omar Torrijos.

Panama's 150,000 government employes, out of a national population of about 2.3 million, provide the bulk of the pro-Noriega demonstrators, Panamanian sources say. Nevertheless, the displays last week seemed to show that the government can control the streets when it wants to.

The opposition to Noriega lacks a recognized leader and appears to be groping its way by trial and error in mounting the protest campaign. In addition, questions have been raised about how far the businessmen and professionals behind the campaign will be willing to go with economic measures that risk hurting themselves as well as the government.

But similar questions were raised about protesters in the Philippines, who expressed their sentiments by throwing yellow confetti out of high-rise office buildings. The generally mild-mannered protests of Marcos opponents left many observers wondering if they could succeed -- until the day in February last year when, spurred by appeals to support the incipient military mutiny, they turned out en masse and sat down in front of Marcos' tanks.