Central American presidents gathered at this religious site today for a two-day summit meeting designed to stimulate regional unity as an antidote to war.

The five leaders faced a June 6 deadline for agreement on the proposed Contadora peace treaty, seen by many Latin American officials as the most effective way to stop the area's guerrilla wars and prevent a broader conflict involving Nicaragua and the United States.

Some officials and commentators have suggested that the gathering here, with the top Central American civilian leadership, represents a last chance to revive the stalled Contadora negotiations, which have been under way since a January 1983 meeting on Contadora Island off Panama. The Contadora talks have been blocked for months by disagreement over arms controls and Nicaragua's refusal to sign a treaty without parallel agreement from the United States to halt sponsorship of anti-Sandinista rebels attacking Nicaragua from bases in neighboring Honduras.

The Nicaraguan position was underlined today by reports from Washington quoting a senior U.S. official specifying that the United States is committed to ending support for the rebels only if a Contadora peace treaty is implemented. A letter over the signature of Philip Habib, president Reagan's special Central American envoy, earlier had linked the end of U.S. support for the rebels only to signature of the treaty, a commitment interpreted by some in Washington as a compromise by the administration.

The presidents of the four nations sponsoring the Contadora initiative -- Mexico, Panama, Venezuela and Colombia -- were absent from the gathering here, site of a Black Christ statue Central Americans traditionally visit for prayer. But the summit host, President Vinicio Cerezo of Guatemala, said the proposed Contadora treaty is the main focus of the talks among Central American leaders Jose Napoleon Duarte of El Salvador, Daniel Ortega of Nicaragua, Jose Azcona of Honduras, Oscar Arias of Costa Rica and Cerezo. It is the first summit of the leaders of all five Central American nations since before the Sandinistas took power in Nicaragua in 1979.

"Esquipulas is a center of faith, and there we have to discuss all our problems, with openness, absolute frankness and even with rawness," Cerezo told a newspaper interviewer recently. In a speech opening the meeting, Cerezo also emphasized that the talks here are not designed to supplant the Contadora forum, but rather to enhance it.