TEGUCIGALPA, HONDURAS, AUG. 19 -- Less than two weeks after the signing of a landmark Central American peace agreement, the signatories' vision of a conflict-free region is becoming clouded with doubts and complications.

The principal reason for the remaining optimism attached to the peace agree- ment appears to be that none of the parties involved wants to be seen as the spoiler. Thus there is some hope that the agreement could roll forward on the momentum produced by the unexpected success of a two-day Central American summit meeting in Guatemala City this month.

At the same time, however, parties to the agreement have started maneuvering with the apparent aim of placing the burden for compliance on their rivals in case of a breakdown.

The major catch of the peace agreement is that many of its provisions are open to differing interpretations.

The agreement, signed Aug. 7 by the presidents of Nicaragua, El Salvador, Guatemala, Costa Rica and Honduras, calls for a cease-fire in Central America's armed conflicts within 90 days in conjunction with amnesties, cessation of foreign aid to insurgencies, prohibitions against the use of one state's territory to attack another and internal "democratization."

The latter provision, primarily aimed at Nicaragua, calls for the lifting of a state of emergency -- the only such decree currently in force in Central America -- and full freedoms for the press and political groups.

Implementing these provisions through follow-up negotiations has been further muddled by conflicting signals from Washington, where the accord was given a lukewarm reception from the Reagan administration and outright hostility from some conservatives.

The right's main complaints are that the Sandinistas cannot be trusted to carry out the concessions they have agreed to and that cutting aid to the Nicaraguan rebels, known as contras, will amount to selling them down the river.

At the same time, the peace agreement has raised the prospect that old divisions could reemerge between pragmatists and hard-liners in the directorates of both the ruling Sandinista National Liberation Front in Managua and the contras' umbrella group in exile, the Nicaraguan Resistance.

The breaking up of an opposition rally in Managua Saturday by Sandinista police and members of mobs known as turbas has prompted speculation that the Sandinistas may not be united behind the peace plan. The incident occurred when several hundred members of the Nicaraguan Democratic Coordinating Council, an internal opposition federation, tried to stage a protest demonstration in the street after inaugurating a new headquarters.

Police with dogs and clubs forbade the demonstration on grounds that the protesters had no permit, and Sandinista youths arrived to scuffle with the demonstrators. The police arrested Lino Hernandez, the head of Nicaragua's nongovernmental Permanent Commission on Human Rights, and Alberto Saborio of the Conservative Party. Both were sentenced to 30 days in jail for "disturbing public order."

The breakup of the demonstration "was a very good first sign that the Sandinistas are not willing to democratize," said Alfredo Cesar, a member of the Nicaraguan Resistance directorate. "But that's not the last word," he added.

Opposition sources in Managua speculated that a faction represented by Interior Minister Tomas Borge, who controls the Sandinista security forces, may be opposed to the democratic changes required by the peace agreement.

The New York Times quoted diplomats in Washington as saying Nicaraguan President Daniel Ortega told Costa Rican President Oscar Arias in a telephone call that one reason he suddenly flew to Cuba last week was to get Fidel Castro's approval for his efforts in order to counter pressures from Sandinista hard-liners.

However, Borge told reporters last week that he supports the "democratization" measures, which he insisted were already in place.

Questions have also arisen about divisions in the six-member contra leadership over the peace agreement. "Without a doubt, the Central American peace plan will put a lot of stress on the {Nicaraguan Resistance} directorate on how best to proceed," said Cesar, one of the members.

Each side in the Nicaraguan civil war argues that the success of the accord depends on the other. The Sandinistas "hold the key and the lock to peace in Nicaragua and Central America," said Ferrey. "Everything is in their hands."

The Managua government, on the other hand, insists that the key factor is U.S. willingess to support the agreement by cutting off aid to the contras.

What appears to be emerging, despite the "simultaneity" stipulated for the peace plan's key provisions, is an attitude among rival parties that their adversaries should make the first move.

The contras, the United States and Honduras, for example, have made it clear that they expect to see some proof of "democratization" by Nicaragua before aid to the rebels is cut off.

According to diplomatic sources, Honduran leaders are worried that a cutoff of U.S. funding for the contras after Sept. 30, when authorization to disburse a current $100 million aid package expires, will weaken pressure on the Sandinistas and force contra fighters inside Nicaragua to retreat across the border into Honduras.

The Hondurans believed funding would go on until the plan's provisions are to take effect Nov. 5, the diplomats said.