These days, Salvadoran government soldiers venture north of this little span only with precaution and well-packed cartridge belts.

In the lush hills beyond, leftist guerrillas have had their way for more than three weeks of a new offensive, controlling five small villages and several roads meandering among the corn and cactus patches south of the Honduran border.

The rebels' prolonged dominion there and in a string of similar hamlets in Chalatenango province to the west is a visible sign that despite increased U.S. aid and military advisers on the government side, El Salvador's insurgent movement remains capable of challenging Army control over small parts of the land and of disrupting economic life with hit-and-run attacks elsewhere.

Salvadoran leaders and U.S. officials insist that the October offensive has fallen short of previous rebel efforts last summer and during elections last March and say the guerrillas have lost momentum against the U.S.-backed Army. But they acknowledge that even diminished rebel successes have served to remind the world that the guerrillas are still out there with enough weapons and munitions to cause trouble for the foreseeable future.

"They have got only publicity, at the cost of increased opposition among the people, to whom they have caused more suffering," the defense minister, Gen. Jose Guillermo Garcia, said in an interview. "In this, they have realized their objective," he added later.

The charred carcasses of trucks and buses burned by rebels litter the Pan-American Highway, cutting through the center of El Salvador, and the main coastal road linking the capital to the rich cotton fields of Usulutan province. Since the guerrilla offensive began about Oct. 10, more than 100 vehicles have been burned in rebel ambushes, during which drivers and passengers were allowed to get out unharmed but were left stranded.

Truckloads of soldiers, fingering their M16s and staring at the brushy roadside, now have to convoy gasoline tankers driving along the Pan-American Highway to San Miguel, the main city in eastern El Salvador. Even so, fuel remains scarce, there and San Miguel's motorists often have to search from station to station to find enough to fill up.

A delegation from the country's cotton growers' cooperative went to see Garcia several days ago seeking similarly increased protection for crop duster pilots, who are taking guerrilla sniper fire during this crucial season for insect control. Maj. Napoleon Hernandez, an officer in the Usulutan district, said one pilot has been killed by a sniper since the offensive began and two others have been wounded, one seriously.

The guerrillas sometimes fire U.S.-made M60 machine guns as the one-seater planes hum down for a low run over the cotton fields, he said, or take potshots with M16 automatic rifles.

Garcia said Salvadoran intelligence had obtained guerrilla plans indicating that they timed their offensive to generate attention for peace proposals announced Oct. 26 in Mexico City in the name of the Farabundo Marti National Liberation Front, the umbrella guerrilla organization, and the Democratic Revolutionary Front, the insurgents' political arm.

"They are trying first of all to tell the world that they still exist," he declared.

Salvadoran and U.S. officials expressed the belief that the rebels' longer term objective is to cause havoc by attacks against roads, bridges, electricity generators, power lines and other economic targets. These officials say the guerrillas realize that they cannot win outright and are seeking to provoke economic hardships as a way of building opposition to the U.S.-backed government of President Alvaro Magana, thus gnawing their way into negotiations.

"The guerrillas know they can't win militarily, but they know that if they wreck the economy, out of the chaos, out of the ashes, could rise a victory," said a military expert assessing the offensive. For that reason, the fast ripening cotton crop in Usulutan province is considered a crucial test of the government's ability to protect economic activity.

The U.S.-trained Atonal Battalion, Hernandez's 900-man unit, has been assigned to the area to help patrol the coastal highway and protect farmers from marauding guerrillas.

"We are trying to give the people a little confidence so they move back and forth," Hernandez said in an interview. "We are trying to give them a little security."

The political results of such attacks against economic targets -- and of the hardship they cause -- are difficult for an outsider to assess. Reactions gathered at random range from the peasant woman in San Vicente who said she "rejoices" when the Army shows up because she then knows her husband is safe, to the yellow-toothed farmhand near here who said the guerrillas have "divisions, divisions among the people."

It is also because the main stakes are now economic, Salvadoran and U.S. officials say, that Garcia's three U.S.-trained "immediate-reaction" battalions have failed to react to guerrilla seizures in this area of Morazan or in northern Chalatenango, where access to a half dozen villages has been under guerrilla control for more than three weeks.

"We have not fallen into the trap of the subversives," Garcia said, adding: "Our objective was to maintain the principal economic activity and leave the rest alone for the time being."

This strategy is in line with advice to the Salvadoran high command from the approximately 50 American military advisers here as part of a $230 million U.S. military and economic aid program, knowledgeable officials said.

Since the offensive began, two of the three U.S.-trained immediate-reaction battalions have remained near their headquarters, Belloso near the capital, San Salvador, and Atlacatl in relatively calm Libertad province to the west. The third, Atonal, was dispatched to Usulutan.

For example, the other two battalions stayed put near their headquarters Wednesday and Thursday, when guerrilla forces overran a garrison at the edge of the town of Suchitoto. The rebels fought for about 12 hours inside the town and cut the main highway to the capital only an hour's drive to the southeast, scattering a series of government checkpoints along the way.

Garcia said he would have intervened in the Suchitoto fighting with rapid reaction troops to open the road faster but he lacked the means. This, he explained, meant chiefly helicopters to lift in reinforcements.

The Salvadoran Army has 19 Huey helicopters. An informed military analyst said only eight were flying during the Suchitoto attack. The others were either under repair, being maintained or were assigned to other duties, he added.

The Army was using one for Lt. Gen. Wallace H. Nutting, the Panama-based head of the U.S. Southern Command, who was here on an inspection tour that included a trip -- by air -- to San Miguel.