SANTO DOMINGO, DOMINICAN REPUBLIC, DEC. 14 -- The first direct cease-fire talks between the government and the rebels of Nicaragua, scheduled to begin here today, were postponed by Managua amid indications of differences among top Sandinista leaders and confusion over the role of an American advisory team, officials and negotiators in Managua, Washington and here said today.

A seven-man rebel delegation, after arriving late yesterday for the second round of cease-fire discussions within the framework of a Central American peace plan, learned only this morning that the Sandinista government had postponed the encounter.

In talks Dec. 2-3 at the Roman Catholic Archdiocese offices in Santo Domingo, the warring sides communicated through a mediator, Nicaraguan Cardinal Miguel Obando y Bravo, without meeting directly. The cardinal insisted on face-to-face meetings to speed things up, and appeared to feel he had prevailed.

In an interview yesterday with the Dominican newspaper Listin Diario, Obando said he had "many hopes" for the meeting, "since it would have been the first time the sides sat down face-to-face."

At a press conference this afternoon in Managua, President Daniel Ortega said the talks had been delayed by "technicalities" related to the role of a four-man advisory team from Washington, originally suggested in November by House Speaker Rep. Jim Wright (D-Tex.) to assist the cardinal's mediation.

Ortega said he met Friday and yesterday in Managua with Obando to settle on the details of the team's participation. But Ortega claimed the rebels, known as contras, had rejected the team's role.

Ortega set no new date for the cease-fire discussions, saying only that they would have to be before a mid-January summit among the five Central American presidents to evaluate the progress of the regional peace accord. The president also said he hoped the talks could be reinitiated in time to achieve a Dec. 24-25 Christmas truce.

Ortega said any face-to-face discussions would include only technical advisers and no officials with decision-making power, and therefore could not be construed as direct negotiations.

Jaime Morales, the contras' chief negotiator, said here that his side is willing to accept any advisers the Sandinistas wish to bring.

In Washington, an aide to Wright said in a telephone interview that the Nicaraguan government contacted the speaker's office last week to relay a request from the cardinal that he would like to have assistance from the team Wright suggested -- including former arms negotiator Paul C. Warnke, retired lieutenant colonel Ed King, and two members of Wright's staff.

However, when Wright's office probed the cardinal's thinking over the weekend, through the papal nuncio in Washington, it was told the Cardinal "welcomed our presence," but did not specifically invite it, the aide said. "That left us with an ambiguity, and we decided not to go," the aide added.

It appeared the Sandinistas were hoping the Americans would be present to buffer any direct encounter between Sandinistas and contras at any level.

Managua's move added credence to reports that Sandinista leaders held back from another meeting with the contras because of their own differences over the goal of the talks.