SAN SALVADOR, FEB. 20 -- Leftist rebels today said they have a plan to "eliminate" U.S. military advisers because of their role in the Army's bloody counterinsurgency war.

In a broadcast over the clandestine Radio Venceremos, Roberto Roca, one of the five commanders of the Farabundo Marti National Liberation Front (FMLN), said the 55 U.S. advisers were taking an increasingly active role in the eight-year-old civil war and they would be punished.

"There is a plan to eliminate North American advisers because they are a direct part of the counterinsurgency effort," Roca said, adding that their participation made them "legitimate military targets."

Roca is leader of the Revolutionary Party of Central American Workers, which took responsibility for killing four U.S. marines at a San Salvador restaurant in 1985.

In the past two months, four U.S. Embassy vehicles have been attacked by suspected rebel urban commandos, but no Americans have been injured.

U.S. Embassy spokesman Jake Gillespie said the threat was no surprise, and "the FMLN has made it clear in the past that U.S. Embassy and military personnel are targets."

Gillespie said that three U.S. military advisers were in the headquarters of the Salvadoran Army's 6th Brigade when it was attacked by the FMLN Wednesday and that the advisers shot back at the attackers in self-defense when their quarters came under fire.

The Army said on Wednesday that only two advisers were at the headquarters, and they were not involved in the fighting.

U.S. advisers here are banned from being in areas where combat is likely to occur, and they may shoot only in self-defense.

Six American military personnel have been killed in El Salvador since the civil war began.

A military attache was gunned down by the FMLN in 1982, four marines in 1985, and one adviser was killed last year when the rebels attacked the headquarters of the 4th Brigade in the northern province of Chalatenango.

El Salvador is a staunch U.S. ally and receives more than $1 million a day in economic and military aid.