MANAGUA, NICARAGUA, NOV. 4 -- As a peace accord begins to take effect Thursday in all five Central American nations, the guns of war are sounding more loudly in the region than they did when the pact was signed three months ago, politicians and diplomats said.

In the 90 days between Aug. 7, when the five Central American presidents signed the pact in Guatemala, and Thursday, the first deadline in the plan's timetable, there has been a torrent of activity by governments seeking to meet its terms requiring cease-fire, amnesty, political dialogue, nonintervention and democratic reforms.

As the plan evolved, its Nov. 5 deadline went from being the last day to comply with the accord to being the first. The five foreign ministers argued at a meeting last week in Costa Rica that it would be premature to assess any government's progress at this time.

The presidents of Guatemala, Honduras, El Salvador, Nicaragua and Costa Rica now agree that they must complete their efforts toward compliance and face a more definitive collective judgment when they reconvene in another regional summit sometime after Jan. 14, 1988.

Many of the moves toward compliance so far have done more to delineate than to narrow differences between governments and the rebels fighting them, or between opposed governments, according to observers.

Since Aug. 7 there have been no fundamental changes in the conflicts dividing three war-torn nations -- Nicaragua, El Salvador and Guatemala.

The Nicaraguan rebels have increased the pace of the fighting and taken their war for the first time into some rural towns in a move to improve their negotiating position. In El Salvador and Guatemala, rebels, disappointed with the breakdown of peace talks, have stepped up their operations.

The peace agreement, written primarily by Costa Rican President and 1987 Nobel Peace Prize laureate Oscar Arias, has achieved more than anyone anticipated the day of its unexpected signing, but less than the peoples of the region had begun to hope for since then.

As of now the consensus among regional observers is that the accord is very much alive -- and very troubled. Arias described its status as "impasse" in public statements last week.

Cardinal Miguel Obando y Bravo, president of Nicaragua's National Reconciliation Commission and one of the region's most influential monitors of the plan, said today: "I believe in the Roman adage that says that hope is the last thing you can lose. So we still have a minimum of hope."

A nagging weakness of the peace plan is that key actors who can make or break the pact are not parties to it: the Reagan administration and the U.S. Congress. The Reagan administration has proposed up to $270 million in military aid to the Nicaraguan rebels, known as contras, for an 18-month period. If Congress voted to allow the aid, the war in Nicaragua probably would escalate. In that case, the leftist Sandinista government has said, it will be forced to reject further compliance, no matter what the other nations decide.

If the five presidents eventually agree that the pact is working, it would strengthen the position of U.S. congressional Democrats who say they want to reject new contra aid. Should they be successful, the region's core conflict could gradually and painfully wind down, leaving the Sandinistas in power.

The conflicts continue in Nicaragua, El Salvador and Guatemala for differing reasons.

In Nicaragua, an estimated 9,000 contras are fighting because they object to the Sandinista National Liberation Front's pervasive political control, collectivist economic policies and alignment with the Soviet Bloc. The Sandinistas reject the contras as U.S.-paid mercenaries whose only goal is to recover properties and powers they lost in the popular 1979 revolt that overthrew dictator Anastasio Somoza.

In El Salvador, President Jose Napoleon Duarte, a centrist Christian Democrat whose popularity has plummeted, remains hamstrung by a hard-line military to his right and about 6,000 guerrillas to his left whose basic demands have not changed in three years of his government.

The Farabundo Marti National Liberation Front, the leftist guerrilla alliance, greeted the approaching deadline with a nationwide traffic stoppage it enforced by burning buses and threatening drivers at gunpoint.

What Duarte now calls the last round of peace talks with the guerrillas collapsed after what was widely considered a resurfaced right-wing death squad assassinated Herbert Anaya, president of a leftist human rights commission, Oct 26.

In Guatemala, the grinding poverty of the majority Indian population and continuing rightist death-squad murders have added new recruits to a decades-old movement of about 2,000 Marxist guerrillas who were almost defeated in the mid-1980s. Both the Army and the guerrillas this month launched the most intense fighting in at least six months.

The most important novelty the peace pact brought was the first joint commitment by the region's five presidents to try to untangle their own problems.

A crucial issue now emerging is whether any leader or organization will have enough authority to give an unequivocal evaluation of compliance that all sides will accept. An international verification commission -- made up of 13 Latin American nations, the United Nations and the Organization of American States -- as well as the national reconciliation commissions in each country are all entitled to express views.

In terms of the letter of the pact, the country that has done the least to comply to date is Honduras, diplomats agreed.

Honduras' main task under the plan is to ensure that the contras stop using its territory to stage their air drops and ground logistical operations and to base their central command. So far Honduras has put no pressure on the contras to move, contra leaders said. It only grudgingly formed the mandated National Reconciliation Commission.

"Honduras will comply scrupulously with the Guatemala accord but we expect Nicaragua also to comply scrupulously," said President Jose Azcona last week in Tegucigalpa. "We are not going to fall into the foolishness of lending ourselves to strengthening a totalitarian system in Nicaragua."

Perhaps the most stress has been laid on the accord's efforts to bring greater political freedom to leftist Nicaragua. Government measures to date have restored some appearances of free expression but the practice of democracy remains sharply constrained, western diplomats and opposition leaders here said.

Opposition politicians complained that the Sandinistas, for the first time in more than two years, called out their turbas, a Spanish term meaning a mob, to harass a small march of political prisoners' relatives in Managua Oct. 22. The turbas are made up of party activists from local block committees.

The opposition insists the government must lift a five-year-old state of emergency nationwide to ensure their freedom of movement. But the government reportedly will lift the emergency Thursday only in some peaceful regions.

"That's just a little candy they're throwing out to sweeten the mouth of some international observer," said Julio Ramon Garcia Vilchez, a politician who leads a dissident faction of the moderate Social Christian Party.

A political dialogue between the opposition and the government, initiated Oct. 5, is haltingly under way, with squabbles at every step. Today, in preparation for what is supposed to be a major peace parade Thursday of Sandinista sympathizers, the streets of Managua are lined with red banners that read, "{Take a} hard line with the Reagan right in Nicaragua."