The Reagan administration, while stopping short of endorsing the peace plan adopted by five Central American presidents last Friday, denied yesterday being hostile to the plan and said it is an encouraging step toward defusing tension between Nicaragua and its neighbors.

The administration tack repeated and elaborated on the cautious welcome afforded to the Central American initiative by President Reagan Saturday.

It also seemed intended to blunt speculation about remarks Sunday by Vice President Bush implying that the administration is suspicious of the Central American plan and considers it inferior to a U.S. proposal put forward by Reagan and House Speaker Jim Wright (D-Tex.) last week.

The strategy, U.S. officials said privately, is to recognize that the plan by the presidents of Nicaragua, Costa Rica, El Salvador, Honduras and Guatemala at least temporarily has displaced the U.S. proposal as the center of attention and that the best U.S. course is to see how it develops before making definitive judgments on its merits or drawbacks.

In following this approach, the administration apparently is seeking to preserve the bipartisan position Reagan has worked out with Wright, who has called for giving precedence to the Central American plan.

The administration also is apparently trying to avoid giving the impression that it seeks to impose its views on the Central American governments and dominate peace talks that might result.

In a radio interview, Bush said the Central American plan favors Nicaragua's leftist Sandinista government over the U.S.-supported rebels in the Nicaraguan civil war and added that the United States would "not leave the contras twisting in the wind, wondering whether they are going to be done in by a peace plan."

Yesterday, White House spokesman Marlin Fitzwater and State Department spokesman Charles E. Redman praised the five presidents' plan as a basis for further negotiations. Fitzwater said the Central American plan "clearly moves the process forward."

"We are encouraged by it," he added. "We think it moves in a positive direction. We want a negotiated settlement in Nicaragua, and we just have to see how the process goes."

Redman, responding to questions about whether the administration has reservations about the Central American plan, referred to Reagan's Saturday statement expressing hope that the initiative would lead to peace in the region and pledged that the United States "would be as helpful as possible" in pursuing that goal.

"The president has spoken to the question," Redman said. "I believe that's very clear . . . . That is the definitive United States reaction."

Redman also acknowledged that the U.S. proposals essentially have been put on the back burner while attention focuses on the progress of the Central American initiative.

"What we're working with now is the plan that was arrived at by the presidents in Guatemala City," he said. He added, though, that "there are probably still lots of ideas in the Reagan plan that are still applicable and that would be interesting subjects for discussion as they work out the details."

A chief difference between the two plans that apparently prompted Bush's critical remarks is the fact that the Central American plan would cut off aid to the contras, while permitting the Nicaraguan government to continue receving military help from Cuba and other communist countries.

The U.S. proposal would bar both sides from getting outside military assistance.