At deadline, peace pact behind schedule but still has momentum. US-Nicaragua standoff remains key. CENTRAL AMERICA

Central America's peace plan is alive, but not kicking as vigorously as its signatories had hoped. When five regional Presidents signed their treaty last August in Guatemala, they pledged that by today they would have laid the foundations for peace.

They were overly optimistic. The five countries have taken only some of the steps called for in the plan. These include political amnesties, dialogue with internal opponents, cease-fires, democratic reforms, cutoff of aid to insurgents, and stopping the use of one country's territory for attacks on another.

And with much left to be done, there are renewed signs of the mutual recriminations that have been in abeyance for the past 90 days. If that bitterness deepens over the next two months, the Arias plan will prove to have been an aberration, rather than the path to peace.

The crux of the problem remains the deep gulf between the Sandinistas and the Reagan administration - the two parties that must come to terms if the plan's objective is to be realized. The Sandinistas insist their revolution is not negotiable and Washington questions the Sandinistas' right to rule.

Yet many diplomats and analysts in the region remain hopeful. ``The momentum is still there,'' one European ambassador says. ``The pact has not been completely fulfilled, but that doesn't mean you can write it off.''

Today, in the first test of the ``simultaneity'' that lies at the heart of the peace treaty, all five Presidents are due to call on outside powers to stop funding irregular forces in the region. That would mean asking Washington to stop aiding the Nicaraguan contras, for example. But US ally Honduras appears hesitant to do so.

``We will have to examine the situation very carefully on Nov. 5,'' said Honduran Foreign Minister Carlos L'opez Contreras last week. ``There is a delicate balance of harmonious interaction'' between each country's moves toward complying with the peace pact, he added.

That was seen as a thinly veiled warning that if the Sandinistas do not comply, Honduras will not feel obliged to do anything about the contra presence on its territory. Under the treaty, Mr. L'opez Contreras reminded reporters, ``countries with armed oppositions are required to offer unconditional amnesties, arrange cease-fires, and to repeal states of emergency.''

Nicaragua has so far shown little sign of meeting those goals. And in a sharply worded message last week, Sandinista comandante Bayardo Arce Castano explained its position: ``The Esquipulas accords demand simultaneous compliance with each and every one of the commitments undertaken.''

``While the aggression organized by the United States continues,'' he warned, Managua was not ready to lift its state of emergency, or decree an amnesty.

Meanwhile, in Guatemala, the peace plan seems badly bogged down. A government team met for three days in Madrid last month with a delegation from the guerrilla forces that have been fighting for the past 25 years. However, no progress was made toward a cease-fire.

Officials have since said they saw no point in renewing talks. They say there is so little fighting in Guatemala, there is no real need for a cease-fire agreement.

Honduras has proved equally reluctant to fulfill its main pledge under the peace treaty: to stop the contras from using its territory to launch attacks into Nicaragua. Indeed, Honduran officials still publicly maintain the diplomatic fiction that they have not authorized the contras' presence.

US officials have leaked suggestions that they are preparing contingency plans to relocate some contras, should their war end. But there has been no sign of action on this front.

Salvadorean President Jos'e Napole'on Duarte, on the other hand, has gone further, decreeing a broad amnesty and holding several rounds of preliminary talks as well as a formal set of talks with the guerrillas on a cease-fire.

Those negotiations had made little progress, however, when they were brutally interrupted by the assassination last month of Herbert Ernesto Anaya, the head of El Salvador's independent human rights commission. His murder was widely blamed on a right-wing death squad. And the Farabundo Mart'i National Liberation Front (FMLN) rebels suspended the peace talks, arguing that Anaya's death had soured the atmosphere too badly.

Though Roman Catholic primate Arturo Rivera y Damas is due to meet FMLN representatives this week to set a new date for further talks, the government appears to be going ahead with a plan to impose a unilateral nationwide cease-fire today. President Duarte was due to announce that decision last night.

This option is also open to the Sandinistas. President Daniel Ortega Saavedra will be addressing a mass rally here this evening to announce whether he will take it.

The Sandinistas' month-old policy of declaring four small cease-fire zones has not encouraged large numbers of contras to hand in their weapons. But their iron refusal to negotiate with contra leaders suggests they may seek an alternate solution, such as a unilateral truce throughout the country.

President Ortega is also expected to announce a new amnesty law, and to hold out the promise of a gradual end to the state of emergency, according to a source close to the government. But both steps ``must be within the framework of simultaneity,'' the source added.

After reopening the opposition daily La Prensa and the Catholic radio station, Radio Cat'olica, ending a ban on political rallies, and opening political dialogue with opposition parties, ``We cannot go on acting unilaterally,'' Mr. Arce warned last week.

By offering the prospect of new measures so long as the US suspends contra aid and Honduras lives up to its word under the plan, Managua would seek to shift attention to its neighbors' shortcomings, officials say.

But while Honduras and Nicaragua both wait for the other to make a move, challenging each other to blink first, the peace pact is in danger of bogging down in a stalemate that could prove hard to break.