TEGUCIGALPA, HONDURAS, AUG. 1 -- After a generally upbeat meeting, Central American foreign ministers have established a working document to use as the basis for negotiations at a regional peace summit next week.

The document is a modification of a plan proposed by Costa Rican President Oscar Arias in February, although there are some key changes that could be sticking points at the meeting Thursday and Friday in Guatemala City.

The only completely new section was one that addressed the refugee problem in the region.

The document was prepared by the foreign ministers of Colombia, Mexico, Panama and Venezuela, who comprise the Contadora Group that seeks a Central American peace accord. They heard suggestions from the five Central American foreign ministers, said one diplomat who asked not to be identified by name or country.

The Guatemala summit was originally scheduled for late June but was postponed after Salvadoran President Jose Napoleon Duarte said more time was needed to prepare a working document for the meeting. As proposed, the Arias plan would have obligated Duarte to negotiate with the leftist rebels fighting his government.

The Contadora Group, named after the Panamanian resort island where it first met in 1983, was invited by Honduras after the Central American nations could not agree on the form preparatory meetings for the summit should take. Direct Contadora negotiations broke down last year.

The foreign ministers are also scheduled to meet Tuesday and Wednesday in Guatemala.

The Contadora nations have been invited to the Guatemala meetings, although it is unsure what role they will play.

As originally proposed, the most important parts of the 10-point Arias plan called for national reconciliation and dialogue between regional governments and unarmed oppostion groups, an immediate cease-fire in all regional conflicts, internal democratization and the suspension of military aid to insurgents.

The United States has objected to the plan because it called for an end of support for the Nicaraguan rebels before the goals of internal reconciliation and democratization were met in Nicaragua. U.S. officials have said they support negotiations to bring about what Washington considers a real democratization of Nicaragua.

The greatest change in the Tegucigalpa document calls for Central American government to open national reconciliation talks within 30 days of the signing of the accord with "all unarmed political opposition groups and with those who are willing to give up the armed struggle."

As written, that would force the Sandinista government in Nicaragua to open talks with the U.S.-backed counterrevolutionaries, or contras, who have repeatedly said they are willing to talk with the ruling Sandinistas. The Sandinistas have insisted that they would not talk with the rebels.

"It is not possible for there to be peace in Central America as long as foreign powers are making war in Nicaragua," said Nicaraguan Foreign Minister Miguel d'Escoto at a news conference at the closing of the meeting.

The change appears to have been taken from a Honduran plan presented at the opening of the meeting yesterday morning.

The Honduran proposal, which came as a surprise to many diplomats, called for a broad restructuring of the timetable for the implementation of the Arias plan. Under the terms of the Honduran plan, aid to insurgent groups would not end until 180 days after signing.

Honduran concerns about the Arias plan have generally run parallel to those of the United States.

"Those proposals I've heard before, from Mr. Abrams and Mr. Habib," said the diplomat, referring to Assistant Secretary of State for inter-American affairs Elliott Abrams and Philip Habib, President Reagan's special envoy to Central America. He would not say whether he believed the United States had helped prepare the proposal.