The United States is considering direct talks with Nicaragua about Central American security issues following the Sandinista government's agreement to discuss a cease-fire with U.S.-backed contra rebels through an intermediary.

An earlier nine-round series of discussions in Manzanillo, Mexico, was broken off by the United States in 1984. U.S. officials have said since then that they would not deal directly with the Sandinistas until Managua agreed to open communications with the contras.

However, senior U.S. officials said yesterday that the United States is reassessing its position in light of Nicaraguan President Daniel Ortega's announcement last week that he had asked his country's Roman Catholic primate, Cardinal Miguel Obando y Bravo, to act as an intermediary in indirect talks with the contras about implementing the cease-fire called for under the five-nation Central American peace agreement. Nicaragua signed the agreement, which was implemented last week and is supposed to be fully in effect by Jan. 4.

Sandinista radio said yesterday in Managua that Ortega will visit the United States Wednesday for a meeting of the annual Organization of American States assembly. There was no indication that he would meet with senior U.S. officials.

U.S. officials stressed that before the Reagan administration responds to Ortega's call for direct U.S.-Nicaraguan talks, Managua's dialogue with the contras must begin and show signs of being serious. In the meantime, officials have indicated that they are holding off until January on a request of $270 million in military aid for the contras.

Even if all conditions are met, the officials said, the United States has not made decisions about the format, context or timing of any talks with Nicaragua. In particular, the officials continued, Washington wants to consult closely with the four democratic countries that are parties to the regional peace agreement: Costa Rica, Honduras, El Salvador and Guatemala.

The officials noted that some of these countries, in particular Honduras and El Salvador, have expressed concern that the United States might reach an agreement with Nicaragua resolving its concerns in the region but not those of neighboring countries.

The United States has expressed particular concern about Nicaragua's military and political ties with Cuba and the Soviet Union and wants commitments that Nicaragua will not receive fighter planes and other sophisticated weaponry from the communist bloc. The Central American countries are more concerned about such issues as the size of the Nicaraguan armed forces and the logistical and other assistance it extends to leftist guerrillas in neighboring countries.

According to the officials, the consultations with the four Central American democracies will begin this week during the OAS assembly, which opens at the Pan American Union Monday. Foreign ministers of all four countries will attend the assembly and the officials said it would be the logical place for high-level talks including Secretary of State George P. Shultz and other U.S. policy-makers.

Following the signing of the peace agreement in Guatemala Aug. 7, Ortega rejected the idea of negotiating with the contras and demanded direct talks with the United States, alleging that Washington controls the contra movement. His government changed its position only after heavy pressure from leaders of the four other countries. Costa Rican President Oscar Arias, principal author of the Guatemala agreement, said that failure to talk with the contras was the biggest impediment to successful implementation of the plan.

The Manzanillo talks were launched following a trip to Managua by Shultz and were conducted between President Reagan's former special envoy for Central America, Harry W. Shlaudeman, and Nicaraguan Deputy Foreign Minister Victor Hugo Tinoco. They were broken off after the United States decided that Nicaragua was using them as a pretext for refusing to reach agreements with other countries in the region.

U.S. officials also are known to have felt that Mexico, the host government for those discussions, was overly partial to Nicaragua. One senior official said yesterday that for that reason the United States will not agree to any future talks with Nicaragua in Mexico.

A well-placed Democratic legislative aide traveling with a U.S. congressional delegation headed by Sen. Christopher J. Dodd (D-Conn.) said in Managua yesterday that administration officials have indicated in recent days in conversations with Democratic legislators in Washington that they are moving toward bilateral talks with Managua.

"That's what everyone is talking about back-channel," he said.

Referring to Assistant Secretary of State Elliott Abrams and other officials, the aide said, "They are prepared to do it {reopen talks}, but they're not sure how or when."

The aide suggested that if a negotiated cease-fire goes into effect in Nicaragua as a result of the proposed indirect dialogue between the government and the contras, Democratic legislators will be in a position to "force" the administration to reopen talks.

Sen. John S. McCain III (R-Ariz.), emerging from the visiting delegation's hour-long meeting with Nicaraguan Vice President Sergio Ramirez, said, "I think those negotiations should certainly not take place until after a cease-fire has been negotiated."

Ramirez confirmed that Ortega will be in Washington Wednesday but said Nicaragua has had no hints of new overtures from the Reagan administration. He said Ortega has not sought any contact with administration officials during his trip and does not expect to have any.

But Ramirez indicated that Arias, the 1987 Nobel laureate, could be a key figure in helping to tie the knot for bilateral discussions.

"There is something now going on concerning the security issues, but no decision has been made on any bilateral talks," Dodd said at a brief news conference just before the delegation headed for the airport. "I think there's a point when the United States will have to participate in security talks, but however you conduct those talks, whether they involve all five Central American countries with the United States participating, I don't think that is something that will happen at this particular juncture."

Staff correspondent Julia Preston in Managua contributed to this report.