For the first time in the decade-old patriarchal relationship between the United States and El Salvador, one that has brought a windfall of $4.5 billion to the small Central American country, Congress has refused to condone the behavior of its brutal armed forces by voting to halve Washington's annual grant of military assistance.

The language accompanying this cut also serves to discourage another offensive by the leftist FMLN guerrillas by threatening to resume U.S. aid if the rebels decide to take advantage of the new status quo and escalate their attacks.However, the crucial issue that remains is whether the surviving $42.5 million scheduled for the Salvadoran military can be used as leverage to promote military reform as well as to ultimately encourage the FMLN to participate in a cease-fire.

Though the congressional action was an encouraging first step, it doesn't necessarily point to a fundamental reformation of U.S. policy toward Central America.

Looking back, White House prospects of obtaining all the requested aid ended when the Salvadoran military stonewalled the investigation of the murder of six Jesuit priests last November.

Armed forces' personnel in charge of the case permitted vital evidence to disappear, and the country's notoriously tainted legal system further undermined already slim prospects that a fair trial, let alone a conviction, would ever take place.

President Alfredo Cristiani, a Washington favorite, has done little to establish to outside investigators that he has the will-power to bring the perpetrators of the crime to justice, particularly since this would involve indicting senior members of his armed forces.

As the congressional action vividly indicated, Cristiani's assertion while in Washington that his government is committed to pursuing the investigation of the killings, no matter where it leads, correctly fell on deaf ears.

The vote should send a clear message to El Salvador's establishment: After a decade of U.S. policy based on the maxim, "they may be tyrants, but they're our tyrants," Washington's public relations efforts to sell the American people the notion that democracy is at stake in El Salvador no longer easily washes.

Congress did not terminate military aid in its entirety for two reasons: First, such an initiative would not have received adequate bipartisan support, and second, because of the perhaps misguided belief that dollars translate into influence that could be used on the Salvadoran armed forces.

Also, Washington is reluctant to give up its rationale for closing its eyes to the reprehensible deeds of the country's military, which not only was involved in the priests' murders, but also in the killings of two U.S. labor advisers and the rape and killings of four U.S. nuns a decade ago.

Even if the guerrillas once represented the red scourge, as the Reagan administration would have had us believe, the complete withdrawal of the Soviet Union from a Central American involvement makes a regional containment policy entirely irrelevant.

While the $1.5 million per day that Washington has sped to El Salvador for the past 10 years may have helped to keep the FMLN guerrillas at bay, the high price for this mission has included not only brutal massacres and daily political assassinations but also the creation of a bloated and corrupt military structure.

The Salvadoran military has cost the U.S. public dearly, even though its prowess has been better aimed at murdering thousands of innocent civilians than defeating the guerrillas.

Unfortunately, democracy cannot function when the figurehead president of El Salvador spends his time snipping ribbons while the country's right wing military leaders are the true arbiters of power.

This is the reason that Congress is trying to break away from an old and bad habit and give peace a chance in Central America.

(Larry Birns is director of the Council on Hemispheric Affairs, a Washington research group. Adam Wolfberg is a research associate.)