President Jose Napoleon Duarte's peace talks with the Salvadoran rebel movement appear to have reached a dangerous impasse, with months of delay likely before any new discussions.

Duarte, who raised broad hopes among Salvadorans as he began a dialogue with the guerrillas in October, said in an interview last night that he is seeking a sign of good faith from rebel leaders before agreeing to the next round of negotiations.

"I don't want to fool around with the hopes of the people," he said. "The answer is simple. They only have to come out and say, 'We don't believe that violence is the way to seize power.' "

Insurgent leaders, at a briefing for foreign correspondents in Mexico City today, called on Duarte to respond to their request for a third session of talks before the end of this month, which they said was forwarded to his government on Jan. 11.

Ruben Zamora of the Democratic Revolutionary Front, the insurgents' political wing, said the rebels suspect that, because of pressure from the right, Duarte is unable to hold any more talks until after March 17 legislative elections. If Duarte's Democratic Party does poorly in the vote, the peace talks could be delayed "six or eight months or even a year," Zamora told Washington Post special correspondent William A. Orme Jr. in Mexico City.

The comments from both sides of the five-year-old civil war provided another reminder that, despite euphoria generated by the initial contact Oct. 15, peace remains a remote hope for the 5 million inhabitants of El Salvador.

The conciliatory atmosphere that surounded Duarte's Oct. 15 meeting with rebel leaders in the hill town of La Palma gave it the appearance of a breakthrough. But since the second session Nov. 30, at which the insurgents presented demands for a new constitution and a reorganized Army, the differences again have become apparent.

Duarte pointed at this gap as the main reason for delay in agreeing to a third round of talks. "They want this government to eliminate itself, to depart from the constitution, to destroy the efforts at democracy and to polarize" Salvadoran political forces, he said. "And you see, what they're asking me is for me to eliminate myself, and if I eliminate myself, with whom are they going to negotiate?"

The main intermediary, Archbishop Arturo Rivera y Damas, had said a third session was likely before the endof this month. But for the last several weeks, Duarte's aides have been warning this is unlikely because of a sour political atmosphere that has hardened right-wing opposition to Duarte's government as the March 17 election approaches.

Duarte said the opposition included attempts by rightist leaders to enlist the Army in a coup d'etat. But the Salvadoran officer corps, after expressing some reservations, endorsed the dialogue effort on an understanding it is to remain within limits defined by the constitution adopted last year, he declared.

For this reason, he added, the talks cannot proceed on the basis of rebel demands presented in the second session. By insisting on a new constitution, a reorganized Army and a coalition government before new elections, Duarte said, the rebels were reverting to hard-line positions held since 1979.

"They're now back again to their tactical dialogue," he declared. "I'm not for that. I said that I want a sincere dialogue. I don't want a dialogue that would only be a show." The dialogue must instead focus on his document presented at La Palma, Duarte added.

This framework for discussions centered on ways to bring insurgents into the political system established by the new constitution, including a proposal for guerrilla combatants to lay down their arms under an amnesty program. The guerrillas have rejected this, equating it with an organized surrender.

Duarte also called on the guerrillas' military branch, the Farabundo Marti National Liberation Front, to halt economic sabotage as a first step toward "humanizing the war." In the last week, guerrilla forces have attacked a coffee processing plant, burned thousands of dollars' worth of cotton in a cooperative warehouse and sought to prevent traffic on the nation's main highways.

"If they really understand that I am trying to obtain peace for the people, for the Salvadorans who are fed up with all this violence, then I'm ready," he said. "I will keep on working on the dialogue."

Salvador Samayoa, a front leader, told Orme that sabotage is the guerrillas' only response to U.S. economic aid, which he said enables the Duarte government to pursue the war. Such attacks also can be effective without causing many casualties, he said.