GUATEMALA CITY, FEB. 19 -- Nicaraguan Cardinal Miguel Obando y Bravo, impatient with the lack of accord on a peace proposal he offered late yesterday, today abruptly suspended a round of cease-fire talks between the Sandinista government and the rebels, placing the future of the negotiations in doubt.

The mid-day decision by the cardinal, the mediator in the second round of face-to-face cease-fire talks between the government and the rebels known as contras, caught both sides by surprise.

Each side immediately blamed the other for the setback, with acrimony that had been absent in earlier cease-fire discussions since December in a Central American peace process. It remained unclear when or how a new round of talks would be scheduled.

Obando, Nicaragua's Roman Catholic primate, appeared to be asserting his authority more aggressively to show that he will not allow the talks to drag on while either side seeks to exploit them to score short-term political gains.

"Since there is no consensus on the mediator's proposal, the mediator believes there is no reason at this time to continue these conversations," Obando said in a statement he read to reporters. He seemed to single out the Sandinista delegation as the one reluctant to accept his five-point proposal.

Obando's plan called for the Sandinista government to free all political prisoners, allow complete freedom of expression, resume a lapsed dialogue with the opposition political parties and reconsider its compulsory military draft law, as good-will gestures to help speed up the cease-fire talks. Obando asked the contras to pull their forces back into special zones for a 30-day truce.

Sandinista negotiators said that only moments after the cardinal unexpectedly stopped today's talks, they handed him a written document sent this morning from Managua accepting his plan in principle.

Sandinista Deputy Foreign Minister Victor Hugo Tinoco, announcing a new concession, also said contra representatives will be allowed to travel to Nicaragua, without accepting a government amnesty, to participate as observers in a dialogue between the government and opposition parties. The contras have demanded three-way negotiations of new democratic reforms, to include their leaders, government officials and the civilian opposition.

Since there was no afternoon session, the Sandinista delegation did not have a chance to present the offer formally to the contras. Jaime Morales, the chief negotiator for the Nicaraguan Resistance, the contra alliance, was taken aback when reporters asked him for his reaction this afternoon.

Paul Reichler, a Washington-based attorney who is a member of the Sandinista negotiating team, said the Nicaraguan delegation consulted by telephone with President Daniel Ortega throughout the night about the cardinal's eleventh-hour proposal.

Reichler said Ortega had responded that he would be willing to discuss all of the proposal's points, including the draft law, directly with the cardinal in Managua. But Ortega said the talks here should be limited to a discussion of the technical aspects of a cease-fire. Last night and this morning the Sandinista delegation guardedly described the proposal as "positive" while they were waiting for the written instructions from Managua, which arrived at noon.

Contra negotiator Morales said the contras accepted the proposal in principle immediately, although this morning he warned that the cease-fire zones Obando had proposed could be a "fatal trap" for contras.

According to Reichler, Ortega also suggested that two separate cease-fire proposals presented by the Sandinista and contra delegations should both be submitted to Roger Fisher, a Harvard Law School professor who specializes in resolution of military conflicts. Fisher, in Ortega's suggestion, would combine the two into a single cease-fire plan for the cardinal to adopt.

Obando stiffly rejected that suggestion today, saying that any cease-fire blueprints should be the work of each side's technical commissions.

Obando complained that neither side had any trust in the other. The government "doesn't believe the Nicaraguan Resistance wants to reach a cease-fire," while the contras "don't believe the government wants to bring democracy to Nicaragua." He insisted that the two sides come to the next round of talks with authority to make decisions on the spot.

Sandinista negotiators said the talks broke down because the contras refused to discuss the details of a cease-fire.