Mexico and Chiapas Rebels Sign Preliminary Accord : Latin America: Concessions on both sides signal a willingness to compromise in later talks, analysts say.

The Mexican government and rebel negotiators took a critical first step Monday toward settling the simmering conflict in the state of Chiapas, signing their first formal agreement since the two sides sat down together in April.

The accord, announced early Monday after an all-night session in the town of San Andres Larrainzar in Chiapas, appeared to do little more than formalize the agenda and procedures for more substantive talks that will begin next month, when negotiators vow to address the root causes of the peasant-backed rebellion.

But both sides gave up major ground in the agreement, which analysts said sends new signals that President Ernesto Zedillo’s negotiating team and the rebel commanders representing the Zapatista National Liberation Army are prepared to compromise to end the 20-month armed rebellion--one that has fueled Mexico’s current political and economic crises.

In a speech soon after the accord was signed about 3 a.m., Chiapas’ Roman Catholic Bishop Samuel Ruiz, a rebel sympathizer, called it “historic.”

He spoke of “real commitments” on both sides of the negotiating table to rid the impoverished southern state of the discrimination and government abuse that the Zapatistas say lie behind their revolt, which began Jan. 1, 1994, with a shooting war that killed at least 145 people.

The agreement--the first positive news from Chiapas since the Zapatistas staged a daylong uprising last December that helped trigger one of Mexico’s worst economic crises--had no immediate effect on the country’s stabilizing financial markets.

In a statement issued just before dawn, the two sides declared that Monday’s accord “marks the start of a new phase in the process of building a just and dignified peace by moving on to the problems that gave rise to the conflict.”

But in later, separate statements, both rebel leaders and Zedillo’s negotiators were more cautious. The Interior Ministry that represents the government at the peace table issued only a one-paragraph statement reporting the agreement, which paves the way for talks on Indian rights to begin Oct. 1.

The ski-masked leader of the Zapatista delegation, who identifies himself only as Commander Tacho, called the accord “the first step on a long road” to definitive peace. “The problems in Chiapas persist. . . . There is no reason to celebrate,” he said.

Outside the 100-year-old building where the latest talks began five months ago, Indian supporters of the rebels--huddled against the rain and cold through the night--applauded their negotiators when they emerged, clad in traditional garb and trademark black ski masks. Monday’s breakthrough marked the end of the sixth round of the often-acrimonious talks.

In the agreement, the rebels appear to have abandoned their demand that the government begin withdrawing the 25,000 soldiers stationed in their mountain strongholds before substantive talks begin.

Zedillo deployed those troops last February in a brief military campaign that restored government rule in more than a dozen rebel-controlled towns, and he publicly “unmasked” the Zapatistas’ charismatic spokesman, Subcommander Marcos, as a veteran leftist without ethnic Indian roots.