SAN SALVADOR, FEB. 2 -- On the eve of a crucial vote by Congress over further funding for Nicaraguan rebels, the leaders of the four nations that signed a regional peace pact with the Sandinista government differ about the impact of the proposed new aid package on the Central American peace process.

While Honduras strongly favors extending the $36.2 million in humanitarian and lethal aid to the rebels fighting inside Nicaragua, the governments of El Salvador, Costa Rica and Guatemala have expressed more ambivalent views on more funds for the rebels, known as contras.

In an interview here, El Salvador's President Jose Napoleon Duarte refused to endorse or oppose further contra aid, saying he could not afford to become involved in the internal decisions of Congress because "this could create antagonisms that might damage my own policies."

Duarte noted pointedly that American economic aid to his government was slashed by $18 million after Marxist-led guerrillas, jailed for gunning down four U.S. marines at a cafe here, were ordered released in accordance with a broad political amnesty under the regional peace agreement.

"Our situation is dramatically sensitive," explained Duarte. "We need help in our country. I feel sorry {the aid cut} happened."

President Oscar Arias of Costa Rica, who was awarded the Nobel Peace Prize for conceiving the peace pact, has muted his earlier outspoken opposition to renewed contra aid, reportedly because of Reagan administration pressure to refrain from becoming involved in the congressional debate. Costa Rica is heavily reliant on U.S. economic aid.

Guatemalan President Vinicio Cerezo has also adopted a low profile recently in the aid debate, although he has been quoted as saying he is not opposed to humanitarian aid for the Nicaraguan rebels.

At a summit in Guatemala last August, the presidents of Nicaragua, El Salvador, Honduras, Guatemala and Costa Rica, all of which have generally good relations with the United States, agreed on measures to end the region's civil wars and "democratize" their countries. The accord called for cease-fires, amnesties for political prisoners and rebels, an end to outside aid for insurgencies and a prohibition on rebels using one nation's territory to attack another country. A second summit last month in Costa Rica urged immediate implementation of provisions not already in effect.

Duarte said that despite U.S. anger over the court order to release of the Salvadoran guerrillas accused of killing the U.S. marines, he felt it was imperative for him to achieve the "moral authority" of adhering scrupulously to the terms of the peace agreement. In so doing, he said, he could insist on full compliance by Nicaragua in order to gain freedom for all political prisoners in that country and halt its support for the Salvadoran leftist rebels.

"If we all comply strictly with the terms of {the} agreement, there will be no need for the contras," said Duarte. "We can only demand compliance within our five countries, but we have no capacity to impose our plan on outer ring countries like the United States, Cuba and the Soviet Union."

The Reagan administration argues that military pressure from the contras has been the main factor pushing the Sandinistas to carry out democratic reforms and negotiate a cease-fire with rebel leaders. This view is largely shared by El Salvador and Honduras.

"Dictatorships never respond to gentleness or weakness," Duarte said in response to a question on Sandinista compliance with the peace accord. "We must be strong and straight."

In a separate interview in Central America, Enrique Bermudez, the military commander of the contra forces, said an aid cutoff would hurt the overall opposition to the Sandinistas and cause some fighters to quit. But he said he believes at least two-thirds of his forces, which he put at 16,000 fighters, would continue the struggle.

"The psychological effect {of an aid cutoff} will not only be felt among the combatants," Bermudez said. It would also affect the contras' civilian support network, he said, as well as opposition political parties, unions and business associations. He said an aid cutoff could prompt Nicaraguans to give up hope of changing the Sandinista regime, end opposition political activities and flee the country as refugees.

In the event of a cutoff, the former National Guard colonel said, "We will have to change our tactics and strategy to adapt to the new situation."

Bermudez declined to elaborate on contra planning for the prospect of an aid cutoff. He said he was unaware of any contingency plans of the Reagan administration.

He rejected a Sandinista cease-fire proposal presented last week as nothing more than a demand for his forces' surrender. Unlike in El Salvador, he said, rebels who take amnesty in Nicaragua "will be integrated into a totalitarian and repressive political system" in which the Sandinista National Liberation Front continues to dominate the Army and the state security apparatus.

Washington Post correspondent William Branigin contributed to this report.