Salvador's rebels wave a peace flag as they win on battlefield

The closer the Salvadorean guerrillas come to military victory, the more they fear a direct United States military intervention. So say close observers of the Salvadorean political scene.

The recently renewed offer by the guerrillas to negotiate a settlement of the Salvadorean conflict was, according to many observers here, prompted by a desire to avoid a military intervention they feared would take place if the Reagan administration thinks that the Salvadorean government is close to collapse. The peace proposals come after several highly successful guerrilla military attacks in the past few months and a reported erosion of morale within the Salvadorean Army.

Representatives of the guerrilla political-military front, the Faribundo Marti National Liberation Front-Democratic Revolutionary Front (FMLN-FDR), proposed direct negotiations with the Salvadorean military. A government would be established in which power was shared between the guerrillas and centrist civilian and military forces. The proposals outlined a relatively moderate, almost Social Democratic, platform for the government. Finally, they said that if the US would not attempt to destabilize the new government, El Salvador's new leadership would not permit Soviet or Cuban troops or missiles on its territory or become involved in subversion of any neighboring countries.

Reaction to the rebel proposals is mixed. The FMLN's reputation is as a group more radical than Nicaragua's Sandinistas, so some observers view the proposals as an attempt to mask the nature of the FMLN's real goals.

Many observers believe, however, that the Army can last another year in the war with guerrillas. Paradoxically, analysts say, this might well increase the probabilities of US intervention.

According to one Mexican diplomat, the probability of US intervention will increase if President Reagan is re-elected.

According to sources, some Christian Democrats and certain segments of the military now are willing to talk with the FMLN about negotiating an end to the war. They worry that the right-wing National Republican Alliance might win the March 25 presidential election - a prospect they think would increase polarization in the country - and they would prefer negotiating with the left to having rightist candidate Roberto d'Aubuisson as president.

A left-of-center Central American, once a top official, says he thinks the rebel peace plan is not a bluff. The heart of the proposal, to him, is the deal the guerrillas want to strike with the US. He believes the rebels would live up to their offer not to destabilize their neighbors or turn the country into an anti-US military base. This observer, who knows the FMLN leadership well, says the rebels have only to look at problems in Nicaragua to conclude there is no benefit in having Cuban military advisers or assisting revolutionaries in Honduras. A deal between the US and Salvador rebels would also get the US out of a bind, since US military intervention would probably involve years of guerrilla warfare, he says.

A somewhat different view comes from Lionel Gomez, former assistant to Rudolfo Vieras, head of Salvador's Land Reform Institute. After Vieras's murder in 1981, Gomez fled to the US. He helped to write the recent Carnegie Endowment Report on Central America.

Gomez, too, thinks the guerrillas feel close to victory and that they fear US intervention. He finds their proposals are rather ingenuous, however, because he says the guerrillas know that the Cubans and Soviets have no intention of stationing troops or missiles in Central America.

Gomez says, ''I think that the people of Salvador would be a lot better off under the FMLN than the present government, but I have basic problems with some of the guerrillas' proposals. They want to purge Army assassins, which is excellent, but are they willing to purge extremists in their own ranks, some of whom have blood on their hands?'' The left, he says, must take a more responsible position and acknowledge its own errors.

Most guerrillas, Gomez aasserts, are good, idealistic people, but extremists among them could wreck any coalition government and thus give a reelected Reagan administration an excuse to intervene. He criticizes the guerrilla proposals for failing to mention elections. ''Have the guerrillas gained the right to make decisions simply because they fought?''

And he theorizes that the Salvadorean Army will be so weak by the time of the US election that El Salvador will be a major campaign issue.