MIAMI, DEC. 30 -- Leaders of the U.S.-backed Nicaraguan rebels said today that they will not attend further cease-fire talks with the Sandinista government until they have a face-to-face meeting with the mediator, Cardinal Miguel Obando y Bravo.

The new demand by the rebels, known as contras, marked the latest round of procedural maneuvering by both sides in the stalled cease-fire dialogue, initiated under an Aug. 7 Central American peace plan.

Both sides are circling this week, each anxious to blame the other for the lack of progress as the countdown for compliance with the peace accord goes into its final weeks before a Jan. 15 evaluation meeting by the five Central American presidents who signed the plan.

Nicaragua's leftist government hoped originally that pressure for peace from the region's governments would force the contras to accept a cease-fire and move Congress to end aid for them. The Sandinistas gambled that they could force the contras to stop fighting without granting them the legitimacy of a face-to-face meeting.

But the contras are emboldened by unprecedented pre-Christmas battle victories and by revived prospects for U.S. aid after a defector's revelations about Sandinista plans to arm up to 600,000 Nicaraguans. They appear to believe that they can benefit if the talks go forward by forcing the Sandinistas to meet with them directly or, if the talks fail, by decrying Sandinista intransigence.

At a midday press conference here, five of the six directors of the Nicaraguan Resistance, the contra alliance, said they expect to meet with Obando next week in Guatemala. Although Obando has met informally with one or two of the directors, it would be the first formal negotiating encounter between the cardinal and the top six contra political leaders. The contras pointed out that Nicaraguan President Daniel Ortega has had frequent planning meetings in Managua with Obando.

The contra chiefs added, however, that Obando told them by telephone yesterday that he was willing to meet them but that Ortega had raised objections. Ortega told Obando yesterday that the government would "lose confidence" in him as a mediator if the meeting took place, the contras quoted Obando as saying. "Ortega threatened the cardinal," charged contra Adolfo Calero.

Agence France-Presse quoted Obando today in Managua as criticizing the Sandinistas for dragging their feet on the peace plan.

"Unfortunately, I have to say the amnesty in its broad sense has not been achieved nor has the state of emergency been lifted, and steps yet remain to be taken toward democratization," Obando said.

After three fruitless attempts at talks in the Caribbean city of Santo Domingo, the two sides are far apart even on protocol matters.

The Sandinistas cancelled at the last moment a second round of talks in Santo Domingo Dec. 14. They sent a foreign advisory team -- Washington lawyer Paul Reichler and West German legislator Hans-Juergen Wischnewski -- to conduct direct meetings with the contras there Dec. 21 and 22.

Managua rejects any face-to-face parley with the contras and believes the peace plan rules out negotiations in any Central American country. The contras, with support from Obando, say direct talks would move faster. In Santo Domingo, they refused to meet with the government's foreign team and reiterated that position today.

"We will not discuss the future of our country with foreigners," said contra leader Alfredo Cesar. However, they did not rule out the possibility of a meeting with Reichler and Wischnewski if a Sandinista government official were present, even if the official did not participate actively.