Escalation in Central America

Henry Kissinger's special commission for Central America is supposed to report to President Reagan in December about what the President calls ''the first real communist aggression on the American mainland.''

But will December be too late?

Mr. Reagan asserts that the Sandinista regime in Nicaragua and the rebel insurgents in El Salvador are being directed from Cuba and the Soviet Union.

Opinions among journalists and among diplomats from most other countries who work in the area raise doubts about the actual degree of Soviet and Cuban involvement.

But there is no serious doubt anywhere about the way the fighting in the two countries is going. Reports from the area, by journalists, by diplomats including Americans, and also from military advisers working with the right-wingers in the two countries, agree that the right-wing cause could be lost before December.

The right-wing ''contras'' who with US weapons, training, and support have been trying for a year now to make a solid lodgment inside Nicaragua, have been able to conduct hit-and-run raids, blow up some bridges, spoil some crops, and kill a few people. But they have not been able to take and hold an important city or portion of the country. They have probably strengthened the regime with the mass of the people. There has been no evidence of a popular inclination to join with the invaders.

In El Salvador where the fighting between right and left has been going on for three and a half years, the government army, in spite of American weapons and training and a 3-to-1 superiority in numbers, controls less of the country today than ever and seems to be incapable of gaining and holding the initiative.

President Reagan has done his best to rouse US public opinion to his cause. But according to the polls the American public continues to be having difficulty grasping the difference between Sandinistas (left) and Salvadoreans (right). There continues to be general public apathy which is reflected in Congress by extreme reluctance to put up more money for the rightists in Central America.

In other words, President Reagan is in a situation similar to the one Richard Nixon inherited from Lyndon Johnson in the later stages of the Vietnam war. He is waging an undeclared war against the government of Nicaragua and the insurgents in El Salvador. He is backing the unpopular side in Nicaragua. Public opinion in El Salvador, so far as it can be determined, seems to want above all an end to war and killing.

American public opinion is not yet as opposed to the war as it was during the later stages in Vietnam. But it has not responded to Mr. Reagan's call for support with any visible, or audible, enthusiasm. Such opinion as there is opposes even the support now going to the factions Mr. Reagan favors, and strongly opposes sending US troops into action.

It is difficult to figure out just how Mr. Reagan is going to salvage his Central American venture under these circumstances. He needs to escalate just to keep his clients going. He will probably ask Congress for more money for guns and for training the ''contras'' for fighting in Nicaragua and the ''Salvadors'' in El Salvador. But to ask for more funds and more authority and not get it would make his problem worse than it already is. It would be demoralizing to his clients.

In the meantime he can order the US Navy to send warships along both east and west coasts of Nicaragua. He has done so. The warships can patrol and discourage by their presence the arrival of weapons to his enemies by sea. But if he orders the warships to intercept shipping headed for Nicaragua, he will be blockading a sovereign country recognized by all other countries the world around. That is an act of war. Under the Constitution he is not supposed to wage war without a declaration of war by Congress - which Congress is not disposed to vote.

Perhaps he will be able to keep his clients going through December without more funds from Congress. Perhaps Congress will dole out a little more help to avoid the danger of being blamed for the loss of El Salvador to ''totalitarian communism.'' Perhaps Henry Kissinger will come up with some wondrous formula to wave it all away.

But meanwhile President Reagan must think enviously of how much easier it is for the people in the Kremlin to run operations of this sort. They have no public opinion or congressional second guessers to interfere with the will and wishes of the leadership.