In the face of U.S. reluctance, Honduras has backed away from demands for a full-fledged security pact in return for its role as mainstay of U.S. military deployment against Nicaragua, the foreign minister said today.

The shift appeared to mark a softening in the Honduran position toward negotiations under way for the last two months in response to a Honduran request for redefinition of U.S.-Honduran relations. These ties have become critical for the Reagan administration's Central American policies and its efforts to pressure the Sandinista government for changes in Nicaragua.

Foreign Minister Edgardo Paz Barnica underlined in an interview that Honduras continues to seek written guarantees that its front-line position will be covered by the full might of the United States despite any possible changes in emphasis in Washington. This reflected fears in the Honduran officer corps that U.S. policy shifts could leave this country exposed after having granted anti-Sandinista guerrillas a safe haven and having permitted large-scale U.S. military maneuvers here for the past three years.

At the opening of negotiations in November, Honduras suggested a mutual defense treaty to replace the current military assistance accord dating from 1954. But the Reagan administration has been firm in telling Honduras this is out of the question since no other country in the region has such a guarantee.

"The government of the United States has been clear that it is difficult for it to subscribe to such a mutual treaty because they have no such arrangement elsewhere in the hemisphere," Paz Barnica told several foreign correspondents.

U.S. officials also have been resisting Honduran demands for some other form of written guarantees, arguing that the Reagan administration's word should be sufficient. President Reagan's national security adviser, Robert C. McFarlane, walked out in a huff from a dinner at the Honduran Air Force base here three weeks ago because Gen. Walter Lopez, the armed forces commander, was pressing him for such commitments on a number of issues, knowledgeable Honduran sources reported.

Despite this incident, Paz Barnica described the negotiations as harmonious and said the Honduran government of President Roberto Suazo Cordova is willing to consider guarantees other than the mutual defense treaty originally proposed.

Honduran and U.S. sources said Honduras seeks some kind of guarantee beyond the oral commitments it has received so far. The Honduran officer corps, with long experience in dealing with U.S. officialdom, realizes that congressional opposition can force a change in administration policies, or that a different administration can take power and abandon informal commitments undertaken by its predecessor, they said.

Paz Barnica said the future of the U.S.-built Regional Military Training Center at Puerto Castilla is one item under discussion. Another, Honduran and U.S. sources said, is the future of anti-Sandinista guerrillas here if Congress refuses to renew U.S. funding for their irregular war against the Nicaraguan government.

Despite the new reticence here, the Honduran military has agreed to a new round of U.S. military exercises. The maneuvers are scheduled to begin later this month, involving as many as 4,500 U.S. troops and, for the first time, U.S. M60A3 tanks and M113 armored personnel carriers, the Pentagon has announced.