Eden Pastora, a hero of the 1979 Nicaraguan revolution and now a leading opponent of the revolutionary government, called the latest attempts to bring him into the ranks of antigovernment groups allied with former soldiers of the Somoza dictatorship "nothing but fireworks."

But a reorganization announced by the generally right-wing Democratic Nicaraguan Forces in Ft. Lauderdale yesterday in an attempt to attract Pastora's allies, if not him, comes as his camp is plagued by doubts.

Earlier this week Pastora waxed philosophical in the late-night quiet of his curtained office among his five telephones, his radios, his topographic maps and his submachine guns on the wooded outskirts of the Costa Rican capital.

"I don't know if it is realism or romanticism," said the exiled Sandinista "Commander Zero" of his efforts to alter the pro-Moscow course of the revolution he helped create.

Frustrations have piled on frustrations since Pastora announced in April that he would force Nicaragua's current revolutionary leaders out of "their mansions and their Mercedes Benz" at gunpoint if necessary.

Potentially he is the most influential opponent of the powerful nine-member Sandinista National Directorate, an authentic hero of the revolution with a mix of machismo and moderation that Nicaraguans find appealing and Washington could probably find acceptable.

He openly despises and is generally despised by anti-Sandinista rebels working with groups of the defeated Somoza dictatorship's National Guardsmen. He fought the National Guard for 20 years and continues refusing to join anyone who was connected with it. He says he wants a leftist revolution and they do not.

What he opposes is the increasing alignment with Moscow and the continued abridgement of basic political freedoms he sees in Managua.

Partly for this Pastora is denounced as a traitor and a Central Intelligence Agency stooge by former comrades he thought would flock to his banner.

But Pastora's revolutionary middle road apparently remains a sketch on the drawing board while the ex-guardsmen and their friends in the Nicaraguan Democratic Forces have built a substantial little army to fight the Sandinistas in northern and eastern Nicaragua.

Except for clandestine radio broadcasts over "The Voice of Sandino," which Pastora openly admits originate in Costa Rica, his organization has yet to take any actions politically, diplomatically or militarily that are even discernible in Nicaragua.

Pastora's people say they are waiting, building up a political organization inside their country and consolidating support for their movement outside. But just this week Pastora and his political allies were rebuffed by a delegation from the Socialist International visiting Nicaragua, Costa Rica and Panama.

When the group of moderate leftist politicians headed by former Venezuelan president Carlos Andres Perez granted him a hurried audience Sunday night, Pastora said he asked them to stop giving the current Nicaraguan government a "blank check" and to quit making excuses for a regime that rigidly censors the press, mocks the electoral process as a "raffle," and is increasingly aligned with the Soviet Union.

"They only listened," he said.

Relations with Washington appear to be a complex no-win proposition for the moment. When Reagan visited here last week, Pastora says he made it a point to leave the country.

"I fled," he laughed.

Alfonso Robelo, a former member of Nicaragua's revolutionary junta and a key Pastora ally, said the Reagan administration, far from aiding them, has moved to thwart Pastora and his group by shutting them off from access to Honduran bases of operation while favoring the ex-guardsmen.

Yet State Department officials hint broadly that they would like to see Robelo and Pastora prosper.

"The people we're interested in are the ones who were in the revolution," said one State Department official as he described the kind of government he would like to see in power in Managua.

The Sandinistas repeatedly charge them with being in the pay of the CIA, but Pastora and Robelo insist that they receive no money from any government.

Although there are at least half a dozen brand-new four-wheel-drive cars outside his office, Pastora guessed that his group has spent in all only $300,000 to $400,000 since his April declarations against the National Directorate.

Hoisting a battered, black Swan 350 D radio transmitter onto his desk, he said even the underground radio station was not expensive, requiring nothing more than the semiportable instrument he was demonstrating, a signal amplifier to boost it from 200 to 1,500 watts and a little cassette recorder to plug in the message.

"Conspiring is cheap," he smiled.

But action is not, and in between comments to a reporter, Pastora dunned old friends over the phone, sometimes seriously, sometimes not.

"We're about down to the bottom of the pocket. We're going to have to rob a bank in Nicaragua," he said. "The problem is, damn, those cordobas Nicaraguan currency aren't worth anything."

Pastora and Robelo both talk of wanting to avoid a fight, but their options are narrowing both because of Sandinista policy and because they have had so little success with other means.

Robelo said that soon the group will begin what he called "demonstrations of presence" in Nicaragua. But the only previous example he cited was an effort in July to block television transmissions of Sandinista anniversary celebrations with a broadcast by Pastora. Only a few households were able to pick it up.

"The fear I have is of an act of desperation," said Pastora, noting growing but unspecified numbers of Nicaraguan peasants joining ex-guardsmen as their only effective means of fighting the steadily tightening grip of the Sandinista National Directorate.