Like a veteran boxer wary of feints and low blows, the Sandinista government is keeping its guard up as it circles a Costa Rican peace plan for Central America. Caution is Managua's watchword as it studies this latest approach to a negotiated settlement. The ``Arias plan'' - named for Costa Rican President Oscar Arias S'anchez, who presented it in January - appears to demand few concessions from the Sandinistas while offering them peace in return. (For plan outline, see Page 12.) But the Nicaraguan government has yet to overcome its suspicions born when President Daniel Ortega Saavedra was excluded from the regional summit that launched the plan.
``I think that they see the Arias plan as another insincere, time-buying effort,'' a senior Western diplomat says.
The authorities here, however, are playing their cards close to their chests. ``We are still in the evaluation stage,'' says Victor Hugo Tinoco, the deputy foreign minister. ``This is one proposal under discussion, but there are definitely other plans and factors that must be taken into account.''
Among alternative plans Mr. Tinoco would like to see on the table is the proposal that Nicaragua put to the secretaries general of the United Nations and the Organization of American States when they visited the region last January.
Central to that proposal was a demand for continued support for the Contadora peace process, sponsored by four Latin American countries, which has appeared stagnant for many months.
``We may not have a signed agreement,'' Tinoco acknowledges, ``but Latin America's role has been determinant in what has been achieved so far. We cannot just throw that into the rubbish bin overnight.''
Nicaragua's refusal to let Contadora be swept aside by newer plans is seen here as a continued effort to offset Washington's influence in Central America.
Government spokesmen say, however, that without US support, no Central American peace effort stands a chance of success.
Though officials here say they are confused by varying comments from US officials as to Washington's exact view of the Arias plan, they clearly remain suspicious of US intentions.
US regional envoy Philip Habib has often expressed his desire to explore a negotiated settlement to the crisis. But, according to Tinoco, ``historically [Habib's] role in trips to Central America has been to give political cover to the real US policy, which has been a policy of war against Nicaragua'' through its funding for the contras.
If Washington were genuinely interested in negotiations, argues the senior Sandinista oficial, it would not be staging its biggest ever military maneuvers next month in neighboring Honduras.
Tinoco rejects the US administration position that such exercises, combined with contra funding, serve to pressure Managua into talks.
He maintains that the war games only ``increase mistrust, and the first obstacle to any negotiations is mistrust.''
``How are you going to negotiate a reduction in your armaments if you have tens of thousands of US troops maneuvering on your border?'' he asks.
Managua's reluctance to state its response to the Arias plan, diplomats here say, stems from expectations that the initiative is likely to undergo modifications before it reaches the negotiating table at a regional summit in Guatemala in June.
``This plan is going to change a lot,'' predicts one Latin American envoy. ``Anything could happen in the next 10 weeks.''
The Sandinistas are understood to be expecting that US allies in the region will propose changes that Nicaragua might find unacceptable.
``I'm not sure they have so much against what is on paper,'' one Western diplomat says of Managua's position. ``But they fear that what is on paper will get tougher at the behest of the United States, Honduras, and El Salvador.''
The Sandinistas initially branded the regional summit that launched the Arias plan as an evil US plot, but they ``were surprised that the plan had so much in it that was discussable,'' the diplomat says.
But the fact that Ortega was excluded from that summit fueled doubts that remain alive here.
``It was an error that went against efforts for peace, not to have invited Nicaragua to that meeting,'' Tinoco argues.
The Sandinistas ``might have thought that this was a really embraceable plan if they had been there,'' the Western diplomat says.
``They would certainly have regarded its sincerity considerably more highly than they do now,'' he says.
The Arias plan Costa Rica's plan would require that: All Central American countries guarantee full observance of civil rights and pluralistic and democratic processes. Free elections be overseen by foreign teams, after every president now in office completes his term. All foreign funding of rebel groups be stopped. All governments facing armed rebellion declare immediate cease-fires and, within 60 days, amnesties. Governments facing armed rebellion hold talks with all internal disarmed opposition groups. A Central American parliament be revived; elections of representatives from each nation be scheduled for early 1988.