A wave of pessimism has swept over the peace talks begun by the government and the rebels in El Salvador. The first round produced a touch of euphoria, but in the second round the two sides presented positions seemingly so unbridgeable as to raise doubt whether the talks can go on. The Duarte government kept to its maximum formula of expecting the guerrillas simply to join its existing political framework, and the rebels demanded not just to share power but also to divide the country into zones of current control. It is suggested that those who do not believe in a political solution are in control in both camps. The would-be conciliators are being left to try to keep the peace process alive by treating the lesser issues of "humanizing" the war -- a Christmas truce, and the like.

But do not be too quick to count the peace talks out. In the first round, both sides took an easy approach; in the second, a tough one. The switch and the all-or-nothing quality of each exchange indicates not so much the implausibility of negotiations as the inexperience of the negotiators. Peace has a public in El Salvador, among citizens of different political persuasions. The peace talks have a constituency among the politicians, who are under pressure to keep the process going. Foreign friends of the two sides, and in particular the nearby Latin countries most interested in winding down the war, will surely keep pressing for talks to continue.

As always, the appearance of impasse becomes itself a factor. Each side would like to project a readiness to stay the course in the battlefield in order to make the talks succeed or to moot them. But it is not only up to the principals; it is also up to the patrons. The record suggests that the impasse will soon produce voices in the United States calling upon the arte government to make the concessions necessary to get the talks moving again.

The Reagan administration should be considering how to preempt this turn. The best way is to ensure the integrity of the elected government against challengers from its right. Specifically, it is essential to bolster President Duarte's efforts to subordinate the armed forces to his office, to keep reducing human rights abuses and to steal the right's political thunder by making the reforms work better. The leader of the extreme right, Roberto D'Aubuisson, was in Washington this week insisting that the talks are dead and that he is the wave of his country's future. President Duarte believes otherwise, and the United States must help him prove so.