House Speaker Jim Wright (D-Tex.), striking a tone of cautious optimism about the peace agreement announced Friday by Central American presidents, urged yesterday that the plan be given a serious chance to work despite its potential shortcomings.

"We have to be supportive of it," Wright said on NBC News' "Meet the Press." "There are a lot of things that can break apart," he said. "A lot of people can be lying to one another. But if you begin with the assumption that it isn't going to work, obviously it isn't."

At the same time, a Nicaraguan foreign ministry spokesman, Alejandro Bendana, said the success of the plan will depend on the "fundamental support of the United States," including an end to military aid to the Nicaraguan contras.

"If we're going to halt the fighting in Central America, that means the United States must halt, in turn, its war against Nicaragua," Bendana said on ABC News' "This Week with David Brinkley." "The Central Americans have gone as far as they can. We now need U.S. concurrence, which is going to make it or break it."

However, Vice President Bush said the United States will not abandon the contras because of the agreement, which he said favors the Sandinista government. "We are not going to leave the contras twisting in the wind, wondering whether they are going to be done in by a peace plan," he said.

In an interview with Miami radio station WINZ, Bush charged that the plan "takes on faith too much of what the {Nicaraguan} communist leader Daniel Ortega wanted" and said the administration may still try to implement the separate peace plan it proposed last week. The administration proposal is explicit in prohibiting Soviet and Cuban aid to the Sandinistas and gives a shorter period for implementation of the terms.

The plan approved in Guatemala City by the presidents of Nicaragua, El Salvador, Costa Rica, Honduras and Guatemala calls for a cutoff of foreign aid to all insurgents in the region within 90 days. Also before Nov. 1, the agreement imposes a cease-fire in all of the region's conflicts, provides amnesty for all rebels who give up their guns and requires democratic reforms in Nicaragua.

While Democratic and Republican leaders agree that the United States should wait until the deadline passes to judge whether the plan has succeeded, they differ over whether Congress should consider renewing aid to the contras in the meantime.

Wright, who helped the Reagan administration develop its separate peace proposal, urged that the administration wait before sending Congress an expected request for as much as $150 million in renewed assistance.

Senate Minority Leader Robert J. Dole (R-Kan.), however, proposed that the administration go ahead with the new request before current aid expires Sept. 30. "If it's not needed, we can always put it back in the Treasury," Dole said on ABC. "Let Congress go ahead and have the money ready in the event this falls through."

Wright and Dole disagreed over whether the Central American agreement limits Soviet and Cuban aid to the Sandinistas. Wright said the plan affects communist aid as much as it affects U.S. aid to the contras, but Dole said the agreement only stops U.S. aid, giving the Soviets and Cubans an advantage in Nicaragua.

The administration has agreed not to pursue aid if a cease-fire goes into effect but has not indicated what it will do in other contingencies. In his most recent statement, President Reagan said Saturday that the United States will be "as helpful as possible" in implementing the peace plan but stopped short of endorsing it, expressing concern that any agreement take into account "the interests of the Nicaraguan resistance."

Wright said yesterday that the role the contras would play in negotiations, which had emerged as a sticking point in peace efforts, has been resolved. He said contra leaders agreed in a telephone conversation early yesterday that the Roman Catholic Church or the Red Cross could represent the contras and the United States in future negotiations.

Costa Rican President Oscar Arias Sanchez, the principal architect of the plan, urged that the United States not dismiss it simply because of doubts that Nicaragua will carry out democratic reforms. Nicaragua will come under "moral pressure from the whole world" to implement reforms demanded by the agreement, he said.