FROM EL Salvador has come a sharp new complaint about the move in Congress to cut military aid. This one is not from the government of El Salvador, which of course opposes the move. It is from the guerrillas. The congressional plan, the FMLN's general command said in its communique of May 2, is ''not enough. Any {emphasis added} assistance to terrorist armed forces only contributes toward war and reduces the possibility for a short-term cease-fire agreement.''

One wonders how this rebuke will be received by House Democrats, who this week went through one more passage of uncertainty on the issue. First they carried a House vote to cut aid by 50 percent or more this year as well as next. But then enough of them crossed over to defeat the parent supplemental bill on final passage, nullifying the aid cut. Feeling perhaps that there are limits to everything, the House mercifully went on to sever the Salvador money from the desperately needed aid for Panama and Nicaragua.

What is the responsible course in El Salvador? To many of the Democrats, and especially to many of the constituents vigorously lobbying them, the right thing is to punish the Salvadoran armed forces for their undeniable failure to stop civilian killings, and to bring murderers of civilians to justice. These are urgent goals. The argument is over how to achieve them. We fear that cutting off military aid could remove American restraints on the army and embolden the insurgents, with the twin effects of increasing the bloodshed and derailing Salvadoran negotiations. The better way to tame the military and -- let us not forget about them -- the insurgents is to bring the war to an end. This requires putting off an aid decision that the House defends as an instrument of subtle pressures on both Salvadoran sides but that both the guerrillas and the government would likely take as a signal of American abandonment.

In fact, a hint of a new mood is settling upon the two sets of talks that touch El Salvador's destiny. The negotiations that the United Nations has just opened between the Salvadoran factions are unquestionably the most serious in the decade-long war. In the talks going on between Congress and the White House, one consideration has been a revulsion for the killings committed under the arm of the Salvadoran military, but another has been a reluctance to spoil a fragile Salvadoran negotiation with a partisan American debate. A cease-fire on agreed terms between the two branches and parties in Washington may be the condition for a cease-fire in El Salvador.