An influential group of Democrats in the House has succeeded in reducing by 50 percent the $85 million President Bush had requested in U.S. military aid to El Salvador's democratically elected government.

The Democrats believe El Salvador has moved too slowly to bring the suspected murderers of six priests to trial.While the government of El Salvador should be encouraged to move on the case as rapidly as permitted by El Salvador's laws, this is the time to strengthen the forces of democracy in El Salvador by providing the level of economic and military aid requested by the Bush administration.

The people of El Salvador should not be punished by congressional Democrats by being left defenseless against still-threatening armed communists and a small but dangerous far right.

Recall that in the autumn of 1989 two groups of extremists launched deadly assaults against innocent civilians in El Salvador: Communist guerrillas infiltrated the cities, used civilians as shields and the combat they initiated resulted in dead and wounded estimated at 1,700 government troops, 2,700 communist guerrillas and 300 civilians.

During this guerrilla offensive lasting for weeks, six priests and their two civilian employees were murdered, and the evidence points to a military faction as responsible.

In assessing current U.S. policy toward El Salvador, it is important to keep the following in mind:

- Free and fair elections held in 1982, 1984 and 1988 attest that El Salvador is building democratic institutions and that these same congressional Democrats were wrong in 1981 and 1982 when they voted against military aid and favored "power sharing" with the guerrillas instead of the elections endorsed by the Reagan administration.

- In November 1989, the president of El Salvador ordered an immediate investigation into the tragic murders, sought aid in doing this from three democratic countries and later publicly alleged that a renegade group of Salvadoran military personnel was suspected of the murders and ordered their arrest.

- The prosecution timetable has been hindered by reported obstructions by associates of the suspects and by the provision of Salvadoran law that an indicted individual cannot be required to testify against suspected co-conspirators. This is a safeguard against state coercion, having a purpose similar to the Fifth Amendment against self-incrimination in the U.S. Constitution.

- Since early this year, President Cristiani has indicated his willingness to negotiate with the communist guerrillas. Yet on May 2, just as the representative of the U.N. secretary general arrived to begin the negotiating process, the communist guerrillas launched attacks on the presidential residence, the home of a Cabinet minister and other places, killing 26 people.

- Cristiani can use U.S. economic and military aid to increase civilian authority over the military and to strengthen the majority of the Salvadoran military leadership who reject the violent methods of an extremist faction; without such aid, the elected president and the cause of democracy will be weakened.

Until the Cuban and Sandinista supplied communist guerrillas cease their efforts to take power by the use of force and accept the repeated invitations of the Salvadoran government and democratic political parties to compete in the electoral process, it is essential that the United States continue to maintain a balanced program of assistance.

(Constantine Menges, who worked on Latin American issues in the Reagan White House, is the author of "Inside the National Security Council." He currently is with the Center for Security Policy.)