Bishop Gregorio Rosa Chavez, a key intermediary between President Jose Napoleon Duarte and the guerrilla leaders who oppose him, warned today that the climate for continuing peace talks had "deteriorated considerably" because of an outburst of violence in recent weeks.

In a homily delivered at San Salvador's cathedral this morning, Rosa Chavez voiced growing uncertainty here about the prospects for a second round of peace talks between Duarte and rebel leaders that was supposed to take place by the end of the month.

"Because of all that has happened in the past few weeks," he said from the pulpit, "the climate for dialogue has deteriorated considerably."

"The date and place of this next meeting," he said, "is not yet fixed."

When Duarte and rebel leaders held their first meeting Oct. 15 in the small northern town of La Palma they agreed to hold a second meeting in the last two weeks of November.

The archbishop of San Salvador, Msgr. Arturo Rivera y Damas, and his deputy, Rosa Chavez, had acted as intermediaries between the rebels and the government to set up that meeting and were to do the same for the second meeting.

Sources close to both clerics have been saying privately in recent days that the scheduling on the November meeting has been held up because of Army and right-wing pressures on Duarte that have been aggravated by renewed fighting in the countryside. The recent fighting resulted in the death on Oct. 23 of Col. Domingo Monterrosa, the Army's leading field commander and, apparently, a key figure in rallying the armed forces behind Duarte's talks with the rebels.

"The right and those officers in the armed forces who are allied with them have argued that in the light of continued fighting in the countryside, guerrilla sabotage and harassment, talks at this time are inappropriate," said one source close to the negotiations.

However, church officials said that they had no doubt that the talks would still be held, even if the timing might not be what had been anticipated.

"The church believes that sooner of later this meeting will be held," Rosa Chavez said after stating that its timing had become "the question of the week."

Duarte hinted Friday that the talks might not be held this month as planned. In a speech before a private business group he said, "If they the talks are a little earlier or a little later, it doesn't matter. It depends on conditions."

Church officials who confirm that they have been a conduit recently for communications between the guerrillas and the government about the next meeting indicated this week that the rebels had proposed to Duarte that the next meeting take place Nov. 27 in San Salvador.

According to the guerrillas' clandestine radio, Radio Venceremos, that proposal was handed over to church officials at a meeting in the countryside on Oct. 30 and apparently presented to Duarte on Nov. 6, when he returned to El Salvador from a brief trip to the United States.

"We are still waiting for an answer to this proposal," the guerrilla high command said in an official communique that Radio Venceremos has been reading during every newscast for the past two days. "The silence of the Salvadoran government makes us believe that its proposal to begin a dialogue in La Palma had more to do with the fundamental necessities of the election of Ronald Reagan than with searching for a way to negotiate a solution to the political, economic and social crisis of the Salvadoran people."

Since the La Palma meeting, both the government and the guerrillas have been flexing their military muscle. Within three days of the La Palma talks, the Salvadoran Army launched a major offensive into northern Morazan province, long a guerrilla stronghold.

It was during that offensive that Monterrosa, the commander of all military forces in the country's eastern provinces, where the guerrillas are most active, was killed in a helicopter crash. The rebels claimed to have shot down Monterrosa's helicopter; the government maintained that it crashed because of mechanical failure.

While the government has continued its offensive in Morazan and launched smaller drives into Chalatenango province, the rebels' other major bastion, the guerrillas have responded with a stepped-up campaign of small ambushes of military patrols, sabotage against electric power lines, one major attack on the town of Suchitoto and interruption of road traffic to the eastern part of the country.

While the Army has refrained from publishing its casualty toll in the five weeks since the La Palma meeting, the guerrillas' radio claimed today to have inflicted 169 casualties on the Army during that period. These, they said, included Monterrosa, another colonel, two majors, two lieutenants and two helicopter pilots who died with him. The guerrillas have not stated their own casualty toll.

There is no way of confirming the guerrilla casualty claims, but the church seems to agree that the numbers have been unusually high in recent weeks.