The Salvadoran Army, frustrated by low levels of action in recent weeks, has lost some of the fighting edge that it gained when it seized the initiative against leftist guerrillas earlier this summer, according to Salvadoran and other military sources.

In addition, some aggressive young field commanders have indicated that they feel they are not receiving the full support they need from their colleagues and superiors to decisively defeat the insurgents. Similar unrest in the officer corps earlier this year led to a mutiny by one commander that resulted in the replacement of the defense minister.

These young officers, who are close to the right-wing president of the constitutent assembly Roberto d'Aubuisson, also are suspicious of the government's efforts to begin a dialogue with the guerrillas, according to a senior government official. D'Aubuisson yesterday criticized the guerrillas for sending low-ranking representatives to their first meeting with the government's peace commission in Bogota, Colombia.

The military sources are not yet alarmed by the sag in the Army's momentum, stressing that the guerrillas still have not seriously challenged the Army's nearly three-month-old offensive. But Western sources acknowledge that the current slack period is showing that the Army still has trouble maintaining its initiative--a primary concern of U.S. trainers here.

Moreover, divisions within the Salvadoran officer corps are deep enough that one commander, Lt. Col. Jorge Adalberto Cruz, accused some of his colleagues of spending too much time at the beach or at home instead of fighting.

"That is why we are not winning the war, because of a lack of conscientiousness," Cruz said in an interview Sunday.

Cruz is commander of troops in Morazan province in northeastern El Salvador, one of the guerrillas' main strongholds, and has been lauded for his aggressiveness by U.S. military officers here.

Under the guidance of its U.S. advisers, the Army in early June launched its strongest offensive in a year. It poured troops into two provinces in an effort to kick out the insurgents there permanently, and began emphasizing small-unit tactics aimed at hunting and killing the guerrillas rather than sitting and waiting to be attacked.

In response, the insurgents have withdrawn to secure bases along the Honduran border or melted into the civilian population, according to Salvadoran officers and other military sources. As a result, there has not been a major battle in a month.

While the guerrillas suffered some losses in the Army's initial assault, they have not fallen wholly on the defensive. Guerrillas based in northern Morazan province repeatedly have penetrated south of the Torola River this month before Cruz's troops chased them back north.

Both Salvadoran and U.S. officials say they expect a guerrilla counterattack sometime this autumn when the rainy season ends. One guerrilla commander was quoted this week as predicting "a general offensive" in September.

Meanwhile, the rebels' withdrawal has left the Army without an easy target.

"The troops have fallen into a kind of boredom. They patrol and patrol and can't find anything," said Col. Jose Dionisio Hernandez, commander of forces in San Vicente province east of the capital. San Vicente, with Usulutan to the south, are the two provinces where the government is concentrating its efforts.

A Western source with close ties to the Salvadoran officer corps listed the Army's problems in the current doldrums as an erosion of its willingness to take risks and of its readiness to chase guerrillas when intelligence reports identify places where they might be. The source could not be identified under the ground rules of the briefing.

This source and Salvadoran officers alike asserted that the troops will quickly regain their morale as soon as combat picks up again.

"One thing that will cure that is a good stiff fight," the Western source said.

One problem simply is that the Salvadoran soldiers, though enthusiastic, are not used to staying out in the field for extended periods, as many have started to do this summer. In addition, lack of helicopters or general inefficiency has hampered delivery of rations to troops in the field. In one case in July, a commander had to tell his troops to forage because he did not have any food to give them.

These difficulties have been compounded by continued dissatisfaction among a feisty group of field commanders in their early 40s who say that some of their superiors and colleagues are lax in pursuing the war.

This dissatistaction erupted in a serious way in January, when Lt. Col. Sigifredo Ochoa rebelled against then defense minister Jose Guillermo Garcia. After lengthy negotiations, in which it became clear that Ochoa enjoyed the support of other officers, Garcia agreed to step down and was replaced later by the current minister, Gen. Carlos Eugenio Vides Casanova. Ochoa was assigned to a diplomatic post in Washington.

In his outspoken comments to U.S. reporters Sunday, Cruz accused some of his colleagues of laziness and preoccupation with politics and money.

"Today is Sunday. If I call some commanders, they're at the beach or at their homes," he said in the small town of San Simon less than two miles from guerrilla lines. When asked which officers he meant, he did not mention names but said as an example that such problems existed in the provinces of San Miguel and La Union.

"I can't criticize the high command for corruption, as Ochoa did, but I'm in agreement with Ochoa on how the war should be conducted," Cruz said.

"When I make requests to the high command , nothing happens. It goes in one ear and out the other."