Why a small Central American country ignites heated debate within the United States; Sandinistas not in Soviet orbit ... yet

Two and a half years after it came to power, Nicaragua's Sandinista leadership has yet to decide just where it is taking the Central American nation.

Despite the Reagan administration's anxieties that Nicaragua is being swallowed into the Soviet orbit, the Sandinistas say they are still striving for political pluralism.

But in the past year they have edged, by their own admission, toward the communist bloc.

It can be argued that this trend results, in part, from growing antagonism between Washington and Managua -- that US policy on Nicaragua has nudged it in the Soviet-Cuba direction.

Top Sandinistas say privately, however, they are mindful of Cuban President Fidel Castro's counsel that they not make the same mistakes he made in alienating the US.

The current visit to Washington of Jaime Wheelock Roman, a top Sandinista commander and minister of agriculture, is evidence of this effort to be on good terms with the US.

Wheelock continues to speak of maintaining political pluralism and a mixed economy in Nicaragua.

Many non-Sandinista Nicaraguans, however, say this promise is honored more in words than actions.

Alfonso Robelo Callejas, a businessman who joined with the Sandinistas to topple the Somoza dictatorship in 1979 and then served with the junta for nine months, is one who says the Sandinistas are edging away from political pluralism.

''Things haven't gone as we expected,'' he said recently.

Robelo urges his former allies to pursue nonalignment -- to restore warmer ties with the US and distance themselves from Havana.

That distance has been shortened recently, perhaps naturally, given the self-proclaimed Marxism of Sandinista top commanders.

Cuba has provided substantial aid to the Sandinistas -- including relief and thousands of educators who helped lower Nicaragua's illiteracy rate from 50 to 12 percent.

The US claims that the Cubans also have provided large amounts of military equipment and training for the new Nicaraguan Army. Mr. Wheelock, asked specifically about US allegations that the Nicaraguans were being supplied with Soviet-built MIGs, flatly denied it and said no MIG deliveries were planned.

He also denied that Nicaraguan pilots are being trained in Bulgaria to fly the Soviet planes.

However, the Soviet and Cuban embassies in Nicaragua are large, and this larger presence is bound to have its impact. But the evidence of Soviet and Cuba control or domination of Nicaragua is spotty and, outside Washington, is seen in knowledgeable Central American circles as inconclusive.