ENDING THE WAR IN NICARAGUA. US and Latin neighbors float own plans for peace. White House initiative complicates work of Central American leaders at key summit

With a distracting bid for a bilateral agreement with Nicaragua, President Reagan has effectively upstaged today's historic meeting of five Central American leaders here. The long-awaited peace talks were supposed to be a triumphant occasion. Nearly six months have passed since Costa Rican President Oscar Arias S'anchez breathed new life into the troubled region's search for peace with his Feb. 15 proposal.

Two scheduled dates to iron out the details of Arias's plan - in May and in June - misfired because of lack of preparation and last-minute complaints by United States-backed El Salvador.

Today and tomorrow, however, the Presidents are expected to reunite and rededicate themselves to a Central America without war.

But the spotlight has shifted.

Tuesday, as the foreign ministers of Nicaragua, Costa Rica, El Salvador, Guatemala, and Honduras were laying the groundwork for the Presidents, word leaked in Washington that the Reagan administration, along with some members of the US Congress, had tentatively proposed a direct opening to Nicaragua.

Yesterday, Mr. Reagan announced a new US initiative aimed at ending the war in Nicaragua and said a plan would be presented at today's meeting. The reported plan offers to delay the US congressional vote on contra funds until after Sept. 30, when the current $100 million package runs out. But three conditions must be met:

An immediate cease-fire for 60 days.

The cutoff of contra military aid in return for the suspension of Soviet military aid and advisers to the Sandinista government.

Rapid moves toward loosening restrictions on the Nicaraguan press and the Roman Catholic Church, and the promise of free elections.

The foreign ministers apparently did not discuss the US actions in their Tuesday meetings. Nor did they venture any definite conclusion about the still-sketchy proposal.

Costa Rican Foreign Minister Rodrigo Madrigal Nieto responded in a conciliatory manner: ``I think it is a constructive proposition,'' he said yesterday morning. ``We are going to review it, study it, see which parts of it can be accepted. I think that a lot of them could be.''

Many other political and diplomatic observers here view the US move as a deft ploy to win more contra aid from a reluctant Congress. If the Sandinistas reject the offer, they suggest, Reagan would have fodder for his pro-contra campaign. Even if the Sandinistas accept it, analysts say, the 60-day period gives them little time to make the rapid progress toward internal democratization and Soviet withdrawal desired by the US administration.

For the Central American countries, the US action - regardless of its implications - only highlights the inescapable influence of the ``colossus to the north.''

Meanwhile, the foreign ministers have reached agreement on three of the 10 points outlined in the Arias plan. Besides settling on a cease-fire and amnesty for all political prisoners within 60 days, the ministers agreed that governments would conduct internal dialogue with unarmed political opposition. Such talks would not include armed rebels such as the contras.

It is still not clear whether the five Presidents will sign an agreement. But even before reports circulated about US maneuvering, several diplomats expressed doubts about the possibility of reaching a meaningful accord.

``It looks a lot worse than it did a week ago,'' says one high Costa Rican official. ``We're back to Square 1.''

According to this diplomat, longstanding divisions between the two basic negotiating blocs - Honduras and El Salvador versus Nicaragua, Guatemala, and Costa Rica - were underscored at a ministers' meeting last weekend in the Honduran capital, when the first group added another peace proposal to the pile. Unlike the Arias plan, which calls for suspension of contra aid immediately upon signing, the Honduran plan proposes to give a six-month grace period before the US would have to cut off aid.

Near the end of the Honduran meeting, foreign ministers of the Contadora countries - Mexico, Venezuela, Panama, and Colombia - pounded out a compromise document, which dropped the Honduran request. But as the sticking point of contra aid is debated here over the next two days, attention will no doubt be diverted by the show-stopping action in Washington.

Key points of Arias plan

The plan's provisions require that:

All Central American countries guarantee full observance of civil rights and pluralistic and democratic processes.

Free elections be overseen by foreign teams, after every president now in office completes his term.

All foreign funding of rebel groups stop.

All governments facing armed rebellion declare immediate cease-fires and, within 60 days, amnesties.

Governments facing armed rebellions hold talks with all internal disarmed opposition groups.

A Central American parliament be revived. Elections of representatives from each nation be scheduled for early 1988.