SAN JOSE, COSTA RICA, JAN. 28 -- Nicaraguan governmental and rebel negotiators today opened their first face-to-face talks on a cease-fire in the Nicaraguan civil war after publicizing new proposals that appeared to have little in common.

The talks began this afternoon in a Roman Catholic seminary on the outskirts of the Costa Rican capital after separate press conferences in which each side discussed its latest cease-fire proposals. The rebels, known as contras, want to negotiate broad political changes in Nicaragua, while the Sandinista government insists on limiting the talks at this stage to agreement on a cease-fire in accord with a Central American peace plan and the Nicaraguan constitution.

The two sides met for about two and a half hours and agreed to meet again Friday morning. The head of the contra delegation, Nicaraguan banker Jaime Morales, said each side had described its position in a cordial atmosphere. "There aren't agreements or disagreements," he said. "The talks have begun in a spirit that could give continuity."

The Sandinista delegation left the seminary without making any statement and could not immediately be reached for comment.

The mediator in the talks, Nicaraguan Auxiliary Bishop Bosco Vivas, said there were points of both agreement and discord during the meeting, but he declined to elaborate. He said he remained hopeful, but that he doubted an agreement could be reached in the "limited time" of Friday's meeting, which is scheduled to last three hours.

Shortly before the talks began, the government delegation made public a 15-point cease-fire proposal that incorporated a plan announced by President Daniel Ortega in Washington in November and amendments issued by the Sandinistas this month in Costa Rica.

The latest Sandinista proposal calls for a truce from March 15 to April 15 in three zones totaling 4,169 square miles in remote, sparsely populated areas of Nicaragua. The zones total a little more than 7 percent of Nicaragua's land area.

"Any armed groups or individuals outside the cease-fire zones may be fired upon, as may anyone who violates the provisions of the cease-fire," the proposal says. While Army troops would be withdrawn from the zones, government officials would reserve the right to move through them to "conduct their ordinary functions."

The proposal also calls for the establishment of six national and international commissions to verify the cease-fire, resolve problems connected with it and "guarantee" the rights of rebels who lay down their arms and accept amnesty.

It says that the contras can keep their arms during the truce, which can be extended by mutual consent. The rebels would be allowed to receive humanitarian aid through a neutral organization once they have gathered in the cease-fire zones.

At the end of the cease-fire period, the proposal says, the contras would "lay down their arms" in designated areas, accept the amnesty and "join in the political life of the nation with full enjoyment of their rights." Then the government would apply an existing amnesty law to free all political or "counterrevolutionary" prisoners except about 2,000 former National Guardsmen not covered by the law.

The Nicaraguan Resistance, the political alliance of the contras, offered a plan calling for "political-military negotiation" on both a cease-fire and democratic reforms. The government, the contras and the internal civic opposition in Nicaragua would take part. This plan proposes that new U.S. lethal aid be placed in escrow for 30 days, during which time the three parties should agree on a truce and a schedule for implementing opposition demands, including proposed constitutional reforms.

It says the cease-fire should take effect at the end of the 30-day period, simultaneous with the democratic reforms. It also calls for "a gradual disarmament of both parties," the repatriation of foreign military advisers, the formation of a "voluntary and apolitical" Army, suspension of compulsory military service, the disbanding of Sandinista militias, demilitarization of rural cooperatives and "a total and unconditional amnesty."

The contra statement dropped any mention of a November proposal that the rebels remain in their "existing military zones," totalling 46 percent of Nicaraguan territory, which would be off-limits to Sandinista forces.

Morales, the contra negotiator,said that a proposal floated yesterday by rebel leaders for power-sharing between the Sandinistas and their internal opposition in a transition government was a legitimate "political aspiration for national reconciliation," but that it was not included in the proposal today.

Vice Foreign Minister Victor Hugo Tinoco, the head of the Sandinista delegation, appeared indirectly to reject the idea of a transition government, insisting that truce talks with the contras be separate from a "political dialogue" with the unarmed opposition in Managua.