The battle lines for what could prove the crucial struggle in El Salvador are being drawn both in Central America and in the United States.
Moreover, the outcome of the growing debate in Washington over El Salvador may be every bit as important as who wins on the Central American battlefield.
As the Salvadoran civil war escalates, with government troops suffering continuing reversals in the fight against leftist guerrillas, the United States appears to be edging toward doing more than it has already done to beef up the Salvadoran Army.
That, in turn, is leading to rising of opposition to US involvement. To many Americans, this recalls the Vietnam protests of the 1960s.
Many American voices are warning against repeating in El Salvador the mistakes of Vietnam. Critics of the Reagan administration argue that El Salvador policy is not very different from Johnson administration policy on Vietnam 17 years ago which led to massive US involvement in the Vietnam struggle.
There has been fresh congressional criticism of the administration's Salvadoran policy recently as three senators and as many representatives aired their views upon returning from Central American familiarization tours.
Several of those legislators, including Sen. Patrick Leahy (D) of Vermont, suggest an immediate reduction in American military aid to the Salvadoran government. While there is as yet no congressional consensus on the aid issue, a toughening stand against US military aid to El Salvador appears to be emerging.
Nationwide opinion polls in recent weeks indicate that people are increasingly questioning the wisdom of stepped up US military aid to El Salvador at a time when the recession at home is deepening. Mail to the White House and to the State Department is running heavily against any further US involvement in El Salvador. The polls also show a public overwhelmingly opposed to sending US troops there.
And more than 350 national and local religious leaders accused President Reagan in a Feb. 21 letter of compromising ''his moral. . . responsibilities'' and called for an end to military aid to the government in El Salvador.
Some American congressmen and former diplomats argue against US support of El Salvador's March 29 legislative balloting. These critics wonder if the elections will, in fact, solve anything since the leftist guerrillas and their supporters are not taking part. Further, they say the polling allows reactionary right-wing demagogues a forum.
But the critics are hard put to offer alternatives, as administration spokesmen point out. Secretary of State Alexander M. Haig Jr. took this tack recently.
While some opponents of current policy urge the US to work for a negiotiated settlement to the Salvadoran struggle, they shy away from answering questions about a Marxist sweep of Central America. Administration spokesmen argue that such a sweep is a distinct possibility if the US does not continue its aid to El Salvador.
Would that lead to the dispatch of US troops even in the face of overwhelming public and congressional opposition?
The administration refuses to be pinned down, preferring to keep all its options open. Secretary of State Haig has not gone so far as some hawks in the administration who say such a US troop presence in Central America is a definite possibility. But hehas declared the US would do ''whatever is necessary'' to prevent the overthrow to the Salvadoran government. ''We have not ruled out anything, and we're not going to,'' the secretary of state said Feb. 2.
The adminstration and Congress are certain to clash if troops are dispatched. At present it is unlikely that Congress would go along with any such troop commitment.
The current US debate on El Salvador is bound have an effect on what happens elsewhere in the region. Indeed, El Salvador is only part of the struggle in the region. The US says it regards events in Nicaragua just as ominously as it does what it sees as a threat of a guerrilla victory in El Salvador.
Over the weekend, attention was diverted from El Salvador to Nicaragua. A suitcase being unloaded from a plane arriving from El Salvador exploded at Managua's airport, killing several people.