It has not happened overnight. But that is no reason for the United States not sounding the alarm on the steady military buildup in Nicaragua with the help of the Soviet Union and Cuba. It naturally provokes concern. According to administration officials, there are at least 1,000 to 1,500 Cuban military advisers in Nicaragua. Some 56,000 tons of military equipment has been shipped there. Nicaraguan pilots now are training in East European countries, and reports are circulating that Nicaragua may acquire advanced MIG-17 and MIG-21 jet fighters.
Not only Washington is worried. Such Latin American neighbors as Venezuela and Mexico also are beginning to be persuaded of the potential threat which this military expansion - together with Nicaragua's apparent slide toward authoritarianism - poses to hemispheric security.
The question is how to deal with that threat.
Fortunately, calm and experienced voices are warning that American military intervention is not the way. Mexico and other hemispheric nations stress that a US military incursion into Central American would violate the charter of the OAS and could only be counterproductive - alienating the people of the region, stirring up anti-US feelings, and playing into Fidel Castro's hands. The Pentagon, too, is reported to be opposed to a US military involvement. Secretary of State Haig, for his part, has not ruled out military actions but seems to be prudently accenting diplomacy, leaving the door open to a restoration of US-Nicaraguan ties. ''I do think there are many strong forces for pluralism and the democratic process in Nicaragua,'' he commented after meeting with Nicaragua's foreign minister, thus backing off from an earlier remark that the Sandinista government is headed toward totalitarianism.
This is not to close one's eyes to disturbing trends in Nicaragua, however. Two years after the revolution the Sandinistas have far from fulfilled their hopes for social reforms, political pluralism, and a mixed economy. It is not clear whether the country is becoming a Marxist-Leninist state or a Western-style democracy. The revolution is still groping. But the jailings of opposition, repeated closings of the newspaper La Prensa, and the flow of power to more radical elements in the leadership cannot but convey the impression of a drift toward dictatorship.
Nicaragua's Latin neighbors and the Organization of American States ought to be exerting quiet pressures on the Sandinista leadership to reverse these trends. It would hardly be conducive to stability in Central America if Nicaragua were to develop into a dominant power bent on fomenting Marxist revolutions in Honduras, Guatemala, and El Salvador, and thwarting such a possibility should not be left up to the United States alone. The onus is on the Sandinistas, moreover, to carry out the idealistic goals which brought them to power and gave Nicaraguans hope that the oppression of Somoza times was truly over. Surely the Sandinistas must realize that the US cannot be indifferent to political developments on its doorstep and that the way to court good relations with Washington is not through suppression of dissent.
As for Cuba, the administration had best be wary of backing itself into a dangerous confrontation. It is no secret that President Reagan would like to do something about Castro, an irritant to the US if there ever was one. But talking him up, tightening the embargo of Cuba, cruising around the island in a show of strength, launching a new radio station (when Voice of America and US radio already reach Cuba) are dubious policies. Even conservative Latin America specialists warn that such actions tend only to strengthen the Cuban leader at home and abroad.
It would be foolish, no doubt, to suggest that Castro could be overwhelmed with kindness. But, inasmuch as shooting it out with him is equally unacceptable, there must be some middle ground where a US-Cuban rapprochement is possible. Instead of toying unrealistically with military solutions which risk a face-off with Moscow, the Reagan administration has a golden opportunity for an imaginative diplomacy that opens the way to a normalization of ties and helps loosen the Cuban-Soviet connection. Such a diplomacy would have to recognize that the revolutionary turmoil in Central America is spawned not by Castroism (which only exploits it) but by the deep popular yearning for social and economic justice. The turmoil will end only when that yearning is addressed.