SAN SALVADOR, OCT. 20 -- The Senate's vote Friday to cut half of El Salvador's $85 million in U.S. military aid is a sharp blow to the Salvadoran armed forces, but in the short term it is likely to have more of a political than military impact on the country's 11-year-old civil war, according to government officials, rebel leaders and diplomats here.

A government statement today sought to put the best face on the Senate action, saying the measure contains provisions that would "support the peace process." The bill calls for restoring all the aid if the guerrillas mount a new offensive or withdraw from negotiations.

However, many officials here say the actual effect of the aid cut would be to hearten the guerrillas of the Farabundo Marti National Liberation Front (FMLN) and dampen prospects of a negotiated resolution to the war. In recent months, U.N.-sponsored peace talks have stalled and rumors of an imminent guerrilla offensive have intensified.

"It's a positive signal for the idea of war, for the military adventure that the FMLN has planned, and it will further prolong the conflict," said Col. Rene Emilio Ponce, the defense minister.

If the measure to slash the aid to $42.5 million survives a threatened veto by President Bush, it would reduce U.S. military aid to El Salvador to its lowest level since 1982. Washington has spent nearly $1 billion since 1980 to bolster the Salvadoran military in the war against leftist insurgents.

The Senate amendment, which followed a similar vote in the House of Representatives in June, was prompted by human rights abuses by the Salvadoran military, particularly the murder of six Jesuit priests last Nov. 16. Cutting half the military aid, one Western diplomat said, could improve the military's human rights performance by making officers wary of losing the remaining $42.5 million in the event of further abuses.

Salvadoran officials, however, have argued that the U.S. aid cut would undermine the government's position and diminish the likelihood of progress in peace talks.

Five rounds of U.N.-mediated talks between the government and FMLN this year have produced only a modest agreement on human rights and virtually no progress toward ending the war. There has been no movement on a central issue in the talks: ridding the military of its worst human rights abusers and prosecuting those involved in the most notorious cases.

The government has said previously that a cut in U.S. military aid would encourage the guerrillas to draw out the war, waiting for the impact of the aid reduction to squeeze the government.

High-ranking guerrillas have belittled the military impact of a 50 percent cut in aid, adding that they will not sign a cease-fire until there is a complete cutoff in assistance.

"I don't think {the reduction} would affect the army fundamentally," Salvador Guerra, a top FMLN commander, said in an interview last week. "If the aid isn't totally cut, then it's certain the war will continue." But another guerrilla, interviewed in northern El Salvador's Chalatenango province last weekend, said: "The less for the army, the better for us."

There are various theories about the effect the reduction would have on U.S. influence with the Salvadoran military. U.S. officials generally take credit for reining in the worst elements of the armed forces, who have been linked to the death squad murders of civilians in the last decade. Death squad activity linked to the military declined sharply in the mid-1980s as U.S. aid -- and influence -- soared.

The worst possible case, some U.S. officials say, is that less aid would translate into less U.S. influence, raising the possibility that death squads would return as part of a scorched-earth campaign to wipe out the rebels and their supporters.

Other officials say that the U.S. presence over a decade has fundamentally moderated the character of the Salvadoran military and that it is unlikely that the rampant abuses of the early 1980s would return even if American assistance were eliminated entirely.

The cut represents a fifth of the country's total military budget. However, President Alfredo Cristiani has vowed to shield the 55,000-strong military and security forces by transferring funds from civilian programs to the armed forces and cutting spending for public works projects and other less urgent areas. Military and security spending currently accounts for nearly a third of the government's budget.

Nonetheless, officials have said that the armed forces have prepared contingency plans for reducing their expenses in the event the government could not find enough money to compensate for the U.S. cuts. The measures would include reductions in the consumption of fuel, large-caliber ammunition, food, spare parts and uniforms.

Even if the military is spared sharp cuts by juggling domestic funds, it could face daunting administrative problems in contracting on its own for spare parts, equipment and munitions that until now have been provided by the United States as part of the aid package, diplomats say. Although there have been suggestions that the Salvadorans were stockpiling arms and equipment from the United States, military officials have denied it.

Moreover, if the government slashes funds from the civilian budget to make up for U.S. military cuts, the impact is likely to be felt by the impoverished majority that the government has tried to woo.

"If the government can't build a road or suspends work on a hospital or never starts an electrification program in some village, that means the guerrillas win, no matter what's going on in the battlefield," one envoy said.

Government officials say they would likely cancel public works projects such as new roads and bridges and try to spare education, health and other social programs.