Managua, Nicaragua — The prickly, adversarial relationship between Nicaragua's ruling Sandinistas and the superpower to their north appears to be moving toward a slightly steadier basis.
After initial conflicting reports, a meeting between Sandinista leaders and the Reagan administration June 25 and 26 is being described by Western diplomats and Nicaraguan officials as a ''businesslike encounter.''
Such sources say it was ''held within a framework of mutual respect'' and confined itself to dealing with technical questions like the time and place of the next round of negotiations. Both Western diplomats and Sandinista officials predict that a second round of negotiations will begin some time between July 19 and the end of the month.
At the same time, Western diplomats have been cheered by reports that the Nicaraguans are proposing Carlos Tunnermann Bernheim, the politically moderate and widely respected minister of education, as their next ambassador to the United States. At this stage, these diplomats say, any positive signs will be helpful in bringing together two countries divided less by any unresolvable issues than by a paralyzing atmosphere of mutual distrust.
The US is making the same four demands of the Nicaraguans that it has made for the past year: (1) withdrawal of East-bloc military advisers, (2) termination of aid to Salvadorean guerrillas, (3) a reduction in Nicaragua's large military forces, and (4) some internal democratization. The emphasis is stronger on the first three points.
In principle, none of these points, especially the first three, is completely unacceptable to the Sandinistas because none of them necessarily challenges either the Sandinistas' control over Nicaraguan society or the revolutionary nature of that control. As pressure on them mounts and their problems multiply, the Sandinistas may be willing to negotiate everything but their power.
The underlying question for the Nicaraguans is whether, even if they give in to the US on the first three points and continue some moves toward democratization, the Reagan administration is willing to tolerate the existence of the Sandinista revolution.
''It's a serious question,'' says a well-placed Sandinista official. ''You have to look at the basic contradiction between the goals of the revolution and US wishes to totally dominate the area. Can the Reagan administration accept the existence of the Sandinista revolution, of Nicaraguan autonomy and sovereignty?''
Some officials of the Sandinista National Liberation Front (FSLN), the official state party, fear that the Reagan administration's four points are only the opening wedge of American demands. Sandinista officials wonder if after asking for the departure of Cuban military advisers, the US will not ask for the departure of all Cuban advisers and the breaking off of all serious ties with the Castro government, or even for the expulsion of civilian Salvadorean political refugees.
Some Sandinista officials wonder if perhaps the Reagan administration's sudden peace moves are not just election-time propaganda. More important, however, they do not discard the possibility that the US might want the talks to fail so it can invade Nicaragua and use the failure of the talks to justify its action.
The Sandinistas' fear of a US invasion also complicates US demands for a reduction in the size of Nicaragua's armed forces.
The underlying US concern is that Nicaragua's revolution is set on a course of inevitable radicalization and further rapprochement with the Soviet Union, thus making impossible any real long-term Sandinista concessions to US demands.
One concern among some members of the Reagan administration is that the FSLN's economic difficulties and slipping popular support might very likely, given the Sandinistas' natural ideological preferences, push the FSLN toward radicalization and complete alliance with the Soviet Union. US officials also fear that the Sandinistas can easily renege on any agreements they make, while the US would find it hard to reactivate the Nicaraguan counterrevolutionaries if they were disbanded.
The negotiating process is made yet more difficult by the fact that both countries will hold elections in November.
According to one politically prominent, left-wing Nicaraguan politician allied with the Sandinistas, several members of the FSLN directorate are pushing for a strong rhetorical attack on US ''imperialism'' during Nicaragua's campaign. These Sandinista leaders believe that a strong anti-US campaign will help rally the population around the FSLN and would also bring more Soviet and East-bloc aid.
This same observer also reports, however, that many influential government ministers and important members of the Sandindista directorate - such as Daniel and Humberto Ortega Saavedra and Jaime Wheelock Roman - believe that negotiations with the US should be pursued very seriously.
Although Nicaraguans could make concessions on the substance of US demands, mutual distrust will complicate the question of the timing of concessions. The schedule of who concedes what, when, and in exchange for what will be difficult.
Nicaraguan officials resist the idea of making any concessions not immediately paralleled by US concessions. They ask several questions: At what point would Cuban advisers be sent back to Havana? In exchange for what US concession? At what point would the Nicaraguan forces be cut back? In exchange for what?
These questions are complicated by the fact that the US may not control the counterrevolutionary forces closely enough to schedule cutbacks in their size and activities to parallel Nicaraguan concessions. Western diplomats in Managua point out that if, as is likely, Congress cuts off all US aid to the contras, this will further reduce US ability to control them.
The US wants to negotiate an agreement that would cover all four demands. Some FSLN officials fear that such a ''package deal'' would take such a long time to negotiate and be so complex that talks would eventually fail. It would be easier, these officials say, to consider individual US demands and negotiate them one by one.
However, according to a Western diplomat, the US would only consider such an approach if it were clear that agreement could eventually be reached on all points. The Amercians, he said, ''would not be adverse to having a phased understanding - where certain things happan at a certain time, one in return for an other, as long as it were clear that the US was biting off on a package deal.''
In spite of all the difficulties and mistrust, however, the attitude on both sides remains a mix of skepticism and hope.
Both Nicaraguan and US officials believe that if the momentum of peace were started, it could strengthen the soft-liners within both the Reagan administration and the FSLN. Peace, they say, is possible.
''If there is a chance for peace, we have to be there, we have to talk,'' said one official who will have an key role on the sidelines. ''It's our moral obligation to do so.''