Despite two key meetings this week aimed at launching talks to end the Salvadoran civil war, senior officials on both sides said afterward that they saw major barriers to a negotiated settlement.

Representatives of the Salvadoran government and its U.S. backers expressed pessimism over prospects for future discussions after leftist opposition leaders reaffirmed their insistence on gaining a position in the government before elections are held. The Salvadoran and U.S. position is that the guerrillas and their political allies must gain political power through the ballot box.

In addition, powerful factions in the Salvadoran Army object to any compromise with the guerrillas and are suspicious of talks with them, according to reliable government sources in San Salvador. On the other side, members of the leftist opposition coalition doubt that the United States is bargaining in good faith, according to leftist leader Ruben Zamora. He said in a telephone interview that the Reagan administration's recent military buildup in Central America was encouraging far-right elements in El Salvador to believe that the United States favored a military rather than a political solution to the conflict.

Finally, both sides say they expect a new guerrilla military offensive in the autumn, which could substantially change the environment in which further talks would be conducted.

In interviews this week, both government and opposition leaders emphasized their willingness to negotiate and their hopes for a peaceful end to the fighting, which has lasted nearly four years. But they were frank about the difficulties involved and appeared skeptical that there was much ground for compromise.

In a comment that seemed to sum up the different parties' views, Salvadoran Christian Democratic leader Julio Rey Prendes said, "At this point I don't see any possibility of getting into an agreement. Nevertheless it is something good to sit down and to start talking." This week saw the most intensive round of negotiations to date on the Salvadoran civil war. On Monday, in Bogota, Colombia, Salvadoran government representatives met for the first time with delegates from the insurgent movement. On the following day, in San Jose, Costa Rica, U.S. special envoy for Central America Richard Stone held his first substantive talks with insurgent leaders.

Participants in the talks agreed that they would not make public details of what was discussed. Both sides said, however, that the Bogota meeting was only a preliminary get-together to arrange for future negotiations. And Zamora suggested that there was little give-and-take in the meeting Tuesday with Stone.

"Each side was laying down its own position," he said.

The two meetings appeared to show that Stone was making progress in his efforts regarding the Salvadoran conflict. President Reagan, responding to congressional pressure, named Stone as his Central American negotiator in April.

But Salvadoran political leaders suggested that the guerrillas were using Stone for public relations purposes, and one high-level source said that Stone's mission was showing few results.

"I think he just likes to travel," the government official said.

Stone started out the week by saying Monday that he was "optimistic" that talks were going in the right direction. By Wednesday, however, he was sounding less encouraged.

The change in tone came after opposition leaders said at a news conference following their meeting with Stone that they still wanted a share of power before they would participate in elections.

Stone told reporters in San Salvador that the leftists apparently were rejecting the democratic process and had given the impression "that they will either be granted power or that they will seize it--I would expect that would be unacceptable not only to the Salvadoran people, but to all the people of the world. I hope that they don't want to say that."

Stone's comments were particularly important because he has said very little publicly since the start of his mission, which is to try to bring together the parties in the Salvadoran and other Central American conflicts.

The president of the Salvadoran government peace commission, who met with rebel representatives in Bogota, echoed Stone's concerns about the rebels' position.

"When they say that they do not want elections organized by the current government , that the only thing they want is power-sharing, and when they talk about a new offensive, then all of this gives the impression that there is not the same interest, not the same desire that we have for talks," Francisco Quinonez said in a telephone interview from his office in San Salvador.

The opposition maintains that their candidates and supporters would not be safe in an election campaign unless the government first brought in representatives of the left and purged far-right elements from the Army and security forces. Right-wing death squads linked to the nation's security forces are widely blamed for most of the estimated 30,000 killings in El Salvador since the civil war began.

But the Salvadoran government has little flexibility to compromise with the leftist opposition because of the Army's position. Conservative officers were "confused" by the government's willingness to meet with the left, according to a senior civilian official in San Salvador. This led to high-level discussions in San Salvador to reassure them that the government was not caving in, the official said.

"The civilians are not yet the ones that control the situation here. The Army still has tremendous power in this country, political power, and in the end the Army makes the decision," said Rey Prendes, leader of the centrist Christian Democrats' caucus in the constituent assembly.

Zamora--a senior leader of the Democratic Revolutionary Front, the political arm of the guerrilla alliance called the Farabundo Marti National Liberation Front--accused the United States of encouraging Army opposition.

"The United States is stepping up its military presence in El Salvador and sending warships to our territorial waters. It's showing the flag all around," said Zamora, interviewed by phone at his home in Managua, Nicaragua.

"Clearly all these signs are sending a message to the most conservative elements in the Salvadoran military and political spectrum that the United States is behind them . . . . We see the U.S. government is telling them: 'Do not go for negotiations; go for the war.' "

Salvadoran government sources and U.S. diplomats in the region believe that hard-line elements in the leftist opposition movement are as strongly opposed to a negotiated settlement as extremist elements at the other end of the political spectrum in the Salvadoran Army. This view has been bolstered by several instances this summer in which different opposition representatives made contradictory statements about the insurgents' position.

Zamora said there was a "unanimous consensus" in the movement on the need for dialogue aimed at a political solution. He indirectly acknowledged, however, that the negotiations might enter the doldrums while all parties await the results of the expected guerrilla offensive and suggested that rebel advances would encourage the government to compromise.

"The development of the war in the past has had a very good effect in convincing people of the need for a political solution," he said.

One sign of the difficulties in the talks was Salvadoran government irritation that the guerrillas sent much higher-ranking figures to meet Stone than to meet representatives of the government's peace commission.

One senior Salvadoran official said the guerrillas had sent "third-rate people" to the Bogota meeting, and Rey Prendes said: "They are trying to demonstrate that the U.S. government is the only important one to talk to."

In this view, the insurgents are trying to boost their own image through high-level meetings with the United States but are reluctant to enter substantive talks with the government.

No dates have been set for future meetings between the insurgents and either Stone or the peace commission.