ALFREDO CESAR, once a senior official of the Sandinista revolution in Nicaragua, agrees with President Reagan that Soviet influence is growing in Nicagagua. Cesar agrees with the Reagan administration about why the Soviet and Cuban influence on the Sandinistas poses a danger to Nicaragua, Central America and ultimately perhaps even to the United States itself.

But Cesar does not agree with the Reagan administration's assessment of what happened to the Nicaraguan revolution, why and how it happened, and what should be done about it. In fact he disagrees strongly with the Reagan policy toward Central America, even while his testimony tends to buttress some of the ominous warnings now coming from the administration's spokesmen, including the president himself.

Cesar's view is one of unique insight and value for several reasons. He is a Nicaraguan who fought with the revolution, sat inside the highest political councils of its government and ran its economy for nearly three years. With the exception of Alfonso Robelo, a businessman who served as a member of the Sandinista junta for its first eight months of existence before bailing out, he is the highest ranking defector to date.

Perhaps most importantly for his credibility, he is one of the few, maybe even the only political defector who has not jumped headlong into the noisy, wheel-spinning world of Nicaraguan exile politics, where numerous groups regularly claim to speak for the Nicaraguan people, pledge to overthrow the Sandinistas, rail against each other and accomplish very little. Until now, he has remained silent, living quietly in San Jose, Costa Rica, where he is paid by the United Nations to help the Costa Ricans reorganize and refinance their debt, something at which he is recognized as an international expert since he did it for the Sandinistas three years ago.

He says he has decided to talk now because he fears his silence has been manipulated by both the Sandinistas and their opposition. And, he says, he has a proposal to save Nicaragua and its revolution from the Marxists, the Soviets, the Cubans and the United States, a proposal that could help stabilize all of Central America.

The Sandinistas, for the record, say they are sorry that Cesar left Nicaragua, and praise his honesty and ability. They insist that the programs he worked for remain intact. "If he wants to come back, he can," said current Central Bank President Luis Enrique Figueroa in a recent interview. "Of course, he has lost the confidence of the government."

In many ways, Alfredo Cesar was an example of the best the Nicaraguan revolution had to offer, and for many who watched the process with sympathy, his departure is symbolic of a larger tragedy.

In 1977, Cesar was something of a prodigy in Nicaragua, the U.S.-educated, 26-year-old general manager of Nicaragua's largest private business, the San Antonio sugar refinery. Politically, he could have been termed left of center, but such terminology did not really apply in the Nicaragua of the 1970s. One was either pro-Somoza, a partisan of the family dictatorship that had ruled for four decades, or anti-Somoza. Cesar, like many of the best and brightest of his generation, was anti.

He began working clandestinely with the Sandinista National Liberation Front in 1977. By 1978, he was a militante, a Sandinista activist, and helped man the front lines during a three-week insurrection that September that brought the first taste of revolution on a nationwide scale. Much to the horror of his upper-class family, he was arrested in Managua by Somoza's National Guard, imprisoned and beaten and finally released in a general amnesty three months later. He fled to self-imposed exile in Costa Rica, where the Sandinista command was planning in earnest the revolution that would drive Somoza from the country forever barely a half-year later.

Cesar organized and directed the team of exiled experts that wrote the Sandinista "plan of government," which promised a program of internal political pluralism, a mixed economy and international non-alignment.

When the guerrillas took over in July 1979, he became "minister of the junta," a cabinet post equivalent to chief of staff. Later, he created and became the first director of the International Reconstruction Fund, the government entity in charge of renegotiating the Somoza-era debt, soliciting new aid funds and channeling the aid at home. He reorganized the newly nationalized banking system in Nicaragua and then became president of the central bank.

He disagrees with the view from the right here, propounded most eloquently within the Reagan administration by U.N. Ambassador Jeanne Kirkpatrick, that what happened in Nicaragua was so predictable and so objectionable that the revolution should have been stopped, even at the cost of continuing to prop up the Somoza regime.

"You can't say, 'Well, this revolution cannot be allowed, because there is a danger it will become dominated by Marxist-Leninists.' Revolutions cannot be programmed or planned. They just happen. And once they happen, you have two options -- you either fight within, trying to support a course that the people of the country want and have fought for, and not leave it totally to the Marxist-Leninists. Or you fight from the outside."

Within the Sandinista organization, even before the victory over Somoza, "there was always a struggle between the nationalist, democratic elements and the Marxist-Leninists. We knew from the beginning that it would continue."

Once the guerrillas became the government, "the whole process of resignations became a process of personal decision. Everybody has a different threshold, a different perspective, endurance or hope or whatever. Some people felt very early that there was nothing to do except oppose it openly. Others, like myself, felt that there were still ways to fight from the inside. Until you reach the point where you can't do anything else from inside the revolution."

For Alfredo Cesar, that moment came one year ago this month. Although he did not resign his job as president of the Nicaraguan Central Bank and leave the country until two months later, there was a day in March 1982 when he knew it would soon be time to go.

He had been on government business in New York when he heard that the Sandinista National Liberation Front had declared a "state of emergency" at home. The announcement followed the dynamiting of two bridges in the northern part of the country by U.S.-backed, anti-Sandinista "counterrevolutionaries." In Managua, the blown bridges were cited as proof of press reports from Washington only a few days before that the Reagan administration had authorized a covert CIA operation against Nicaragua.

Cesar rushed back in time for the first meeting of a new emergency committee of highest level government officials, including himself, who were secretly designated as a sort of government within the government to run the country during the emergency. The committee's existence was never announced, and its duties were never clearly spelled out. But it soon became apparent, Cesar says, that its establishment, and the measures it took -- over his objections and those of others in the minority -- meant that the balance of power had shifted within Nicaragua, and that a battle begun within the revolution many years before had been lost.

The committee militarized transportation and communication; trucks, tractors and radios on private farms were expropriated for the defensive needs of the state. Agro-businessmen, still only half-convinced that the Sandinistas were to be trusted, reverted to overt hostility. Cesar says that a production incentive program for private enterprise, painstakingly put together and finally approved by the Sandinista high command just months before, was quietly shelved. Confiscation of private holdings was stepped up.

Cesar now believes that Marxist-Leninists within the Sandinista leadership were lying when they promised a pluralistic, democratic government and a mixed economy to replace Somoza, and were only waiting for the right moment -- and the right excuse -- to take over what was a "nationalist, democratic revolution." Those who were not lying, a group Cesar calls the "nationalists," now have been willingly or unwillingly co-opted to the Marxist view, or have left the country. Those who remain at the upper levels, he believes, are a collection of doctrinaire ideologues, blind to any reality but their own, increasingly and tragically allied to the Soviet Union and its friends and ever more opposed by the Nicaraguan people.

In the beginning things went relatively smoothly, with large amounts of aid pouring in from the West and business confidence growing. The rise of Marxist-Leninist influence was a gradual evolution that began in 1981, Cesar says, as proponents of the Soviet Marxist line, principally Planning Minister Henry Ruiz and Interior Minister Tomas Borge, pushed for a policy or program but still often lost within the nine-member Sandinista directorate. The others, he says, generally supported his efforts to build confidence in the private sector.

The beginning of 1981 also brought the inauguration of the Reagan administration, which quickly cut aid and accused Nicaragua first of promoting and aiding revolution in El Salvador, and then of intolerable internal repression of its own population. "The aggresive policy of the U.S. administration has been a terrible mistake," Cesar said, "because it has given the Marxist-Leninists enough arguments to push their line, using the nationalism of the Nicaraguan people."

Cesar believes administration attempts to use the Soviet threat to justify complaints about the internal dynamics of the Nicaraguan revolution and its aid to El Salvador, and the Sandinista efforts to use the U.S. threat to justify internal repression, are cut from the same Machiavellian cloth.

There are two separate Nicaraguan problems today, he insists. The first is an external one -- the introduction of a substantial Soviet-Cuban presence into a nation that is clearly within the American sphere of influence. The United States and the Latin American nations, have the right to be concerned and to "ask Nicaragua not to endanger the security of the hemisphere," Cesar says. The way to cope with this is diplomatically, not by intervention, he adds. "There are a series of agreements, country to country, to deal with the security problem that the Soviet presence in Nicaragua poses for the hemisphere."

Latin American and Western European countries concerned about both U.S. and Soviet intervention, he suggests, should offer their own strong support as a neutral alternative. "To say, 'We support the Nicaraguan revolution. We reject the Soviet presence there. We're not asking you to defend yourself (against the United States). We will support you, our armies will defend you.' And once you take away the Soviets, you're dealing with a Latin American problem, not a problem of the superpowers, and you go to Washington and say, 'You have no more reason to be against Nicaragua.' "

That change, Cesar says, would give the Nicaraguan people the chance to solve the second problem, the internal one, on their own. Cesar says he speaks not of restrictions on press freedom and postponement of elections, issues he believes are secondary in the minds of most Nicaraguans, but of perversion of the revolutionary goals that Nicaraguans fought for -- land for the peasants, worker participation in the factories, and a secure future for private enterprise as well.

Cesar speaks with a kind of wistfulness that is painful to hear, of aatime he clearly remembers as a triumph of a noble people against insurmountable odds, when the Nicaraguan revolution was the world's darling. The Nicaraguan people once turned around their own fate, he says, and they could do it again, if given the chance.

Karen DeYoung, foreign editor of The Post, covered the revolution in Nicaragua.