Secretary of State George Shultz is on a whirlwind tour of four Central American nations this week, trying to find a way to get the Sandinista-Contra peace talks off dead center. His chances of success look bleak.

The talks ended in stalemate earlier this month, and the 13-week-old truce in Nicaragua could be falling apart. While fighting has not resumed, the signs look ominous.The Contra rebels reportedly are filtering back into Nicaragua from Honduras, and the Sandinistas have called a meeting of military officers to discuss tactics and strategy.

However, the Contras lack the military muscle to carry on much of a fight since Congress canceled military aid. The possibility of such aid being renewed does not look promising.

Without such aid, the Contras have little bargaining power. The Sandinistas have made gestures of democratic reform, but the reforms appear to be superficial at best.

The Sandinistas still hold an estimated 2,000 political prisoners and still routinely arrest people for expressing dissenting political views. And the regime still censors the news media. That's hardly an encouragement to the Contras to lay down their arms.

In addition, the Soviet Union has poured hundreds of millions of dollars of military aid into Nicaragua since the regional peace plan was promoted nearly a year ago. The Sandinistas are getting militarily more powerful, while the Contras are getting steadily weaker.

Against this backdrop, Shultz is visiting Costa Rica, Honduras, Guatemala, and El Salvador to get some consensus on what to do next. Little vigorous response is expected. The trip to El Salvador is particularly unlikely to produce strong commitments on Nicaragua because El Salvador has its own problems. They include a leadership vacuum caused by the terminal illness of President Jose Napolean Duarte, and the increasing polarization of the country between leftist rebels and rightist forces that have made recent gains in government power.

Shultz is to be commended for his untiring efforts, but the basic problem lies with Congress. Unless the Contras have some bargaining chips in the form of military aid, the Sandinistas can be expected to sit tight and refuse to make democratic reforms called for in the regional peace plan.