Three days after President Reagan revealed his new peace initiative for Nicaragua, the proposal's principal effect has been to create massive confusion about the meaning of the plan and its chances of resolving tensions in Central America.

Judging by the initial reactions, the plan's promises and pitfalls look very different depending on whether they are viewed from the perspective of the Reagan administration, the leftist Sandinista government of Nicaragua, the U.S.-backed contras fighting the Sandinistas or the other countries of Central America.

Even here in Washington, the White House's portrayal of the plan as a bipartisan effort between the administration and House Speaker Jim Wright (D-Tex.) has not been without some discordant notes. In discussing key aspects of the plan, Wright and some administration officials have sounded at times as though they were talking about different -- and contradictory -- things.

At issue is whether the initiative can bridge the vast gulf between the Sandinista government, which believes it has a mandate won in long years of guerrilla warfare against a rightist dictatorship to transform Nicaragua into a revolutionary state on the model of Fidel Castro's Cuba, and the Reagan administration, which has backed the contras out of fear that the Sandinista agenda includes making Nicaragua a base for communist subversion in the hemisphere.

The spillover from the conflict has exposed Nicaragua's neighbors to a cross fire of ideological pressures from both Managua and Washington. On the domestic American political scene, arguments about the wisdom of supporting the contras have caused a division in Congress so deep and bitter that Wright, as he told reporters Thursday, felt compelled to buck the skepticism of most House Democrats and test whether the administration now is sincere in seeking a diplomatic rather than a military solution to the dispute.

Since Wednesday, when Wright appeared at the White House with Reagan and Secretary of State George P. Shultz for the unveiling of their new bipartisan initiative, the rush of events has left unclear whether the plan can survive the danger that the parties to the dispute will try to abort it or turn it to their partisan advantage.

To Nicaraguan President Daniel Ortega, announcement of the plan was an opportunity to call for immediate, bilateral talks between his government and Washington. But Shultz spurned that, saying the United States will not abandon a regional approach and "sit down with Nicaragua to decide what is right for Central America."

To complicate matters further, the presidents of Nicaragua, Costa Rica, El Salvador, Honduras and Guatemala, meeting in Guatemala City, reached agreement yesterday on a peace plan based on proposals made earlier by Costa Rican President Oscar Arias.

What effects that will have on the Reagan initiative were not immediately clear. However, Wright, who said he had been told of the Guatemala agreement in a 4:30 a.m. phone call yesterday from Costa Rican Ambassador Guido Fernandez lauded the Central American presidents' action and said he believed the United States should be "cooperative and supportive" of it.

Despite Wright's optimistic assessment, it was unclear whether the plan adopted in Guatemala contains features of the original Arias proposal that the administration regards as unacceptable and sought to circumvent when it came up with its own plan.

According to the reports from Guatemala, the accord reached there establishes a commission of the foreign ministers of the five countries. It is to convene within 15 days and, within the ensuing 90 days, negotiate a cease-fire to all regional conflicts, an agreement by the five countries to halt aid to insurgents seeking to overthrow any government in the region and a document outlining civil and political rights which each country would be obligated to adopt at the time the cease-fire goes into effect.

This runs counter to the Reagan proposals in several key aspects. For one thing, the Reagan plan calls for reaching agreement on a cease-fire within 60 days. That timetable would end Sept. 30 when the current $100 million in contra aid runs out, thereby putting the administration in a theoretically advantageous position to ask Congress to renew contra funding if a cease-fire agreement with Nicaragua has not been achieved.

Wright said he has been assured by the administration that the 60-day limit on negotiations is not merely a ploy to demonstrate Sandinista recalcitrance and win more votes in Congress for contra aid. However, senior administration officials have insisted -- in the face of congressional skepticism that 60 days is an unrealistically short time to negotiate a cease-fire -- that they will not yield on that timetable.

In addition, the Guatemala agreement apparently would cut off outside aid only to insurgent forces such as the contras, while the U.S. initiative specifies that Nicaragua must also stop getting military aid from Cuba, the Soviet Union and other communist bloc countries. In fact, the principal differences between the original Arias plan and the U.S. initiative involved what U.S. officials called "simultaneity" -- the idea that an American disarming of the contras must be matched at the same time by Nicaraguan moves to uphold their obligations under the agreement.

The Arias plan appears to be vague about when Nicaragua would have to take steps toward democratization. The U.S. proposals specify that as soon as a cease-fire goes into effect, Nicaragua must immediately restore civil liberties, suspend the emergency law giving it arbitrary police powers and establish an electoral commission to prepare the way for regular elections.

Some U.S. officials also have said that the contras must have a role in negotiating the cease-fire, and it must be acceptable to them before the United States halts their aid. That seemed to place them at odds again with Wright, who told reporters Thursday that the contras did not necessarily have to be direct participants in negotiations but could be represented by mutually acceptable third parties, such as Roman Catholic Church represenatives. But Shultz in testimony on the Hill yesterday expressed the view that the Catholic Church would be an acceptable intermediary if the Sandinistas and contras cannot sit down together.

Whether the apparent differences between Wright and the administration will be smoothed out sufficiently to keep their partnership intact should become clearer as the administration confronts the compromises that undoubtedly will be required to gain serious consideration for its plan.