Castro would edge away from Moscow -- if

Earlier this year, a news story circulated that the then United States secretary of state had privately described Cuban President Fidel Castro as ''anguishing'' over an unspecified US offer that could lead to both a rupture in Cuban-Soviet relations and an improvement in Cuban-American ones. If indeed Castro does decide to break away from the USSR, Moscow would lose an important ally that in the past has worked to advance Soviet interests in Africa and Latin America.

But will a serious rift between Moscow and Havana actually take place, or were the reported comments merely wishful thinking?

There are important strains in Soviet-Cuban relations. The most serious of these lie in bilateral relations: The USSR has not made as strong a commitment to Cuba's defense as Castro wants. While the USSR has signed treaties of friendship and cooperation with several nations in Asia and Africa, there is no defense pact between Moscow and Havana. In addition, the Cubans are dissatisfied with many aspects of Soviet economic assistance. In the foreign policy realm, Soviet actions in Afghanistan have embarrassed Cuba in its attempt to convince third-world nations that the USSR is the natural ally of the nonaligned movement.

Nevertheless, the ties that draw the Soviet Union and Cuba together are stronger than the forces which could drive them apart. Both nations share a Marxist-Leninist ideology, encourage Marxist revolution in the third world, are working to build a socialist economy and defend the socialist order in Cuba, and are hostile toward as well as fearful of the US.

Previous rifts between the USSR and other communist states developed mainly in terms of their own bilateral relations without much reference to the US. It might be thus argued that, if a Soviet-Cuban rift is to take place, it will do so without American encouragement.

However, Cuba fears the US more than does perhaps any other present or former Soviet ally. In his 1978 interview with Barbara Walters, Castro made it clear that even after being in power for close to two decades he blamed almost everything that went wrong in Cuba on the CIA. As a result, it is doubtful that Cuba would ever break relations with the USSR unless some degree of cooperative ties were first established between Washington and Havana.

There are several circumstances under which Cuba might wish to become more independent of the USSR if Cuba knew it could move closer to the US:

1. In 1986, Cuba must begin repaying its massive debt to the USSR. It is possible that fairly serious Soviet-Cuban disagreements may occur over both repayment and the level of Soviet economic aid to and trade with Cuba. Friendlier relations with the US could allow Cuba to lessen its almost complete economic (and hence political) dependence on the USSR.

2. Castro is striving to maintain his leadership position in the nonaligned movement. If the USSR ever took action against or invaded another third-world nation, Castro might be forced to choose between remaining a Soviet ally and continuing his leadership role in the third world. Friendlier ties with the US might induce Cuba to move to the latter position and away from the former.

3. Castro and his brother Raul have been the dominant figures in Cuban politics from the revolution up to the present. It is not clear who will eventually succeed them. In the post-Castro era, the Soviets may attempt to acquire much greater control in Cuba than they have now. This could alienate many new leaders who might then be more willing to turn to the US than is Castro. In such a case, it would be crucial for the US to have some influence in Cuba already. If not, the USSR would be able to act much more rapidly than the US.

While it is therefore doubtful that Castro wishes to change alliances in the immediate future, he would prefer to be more independent of Moscow. This is a development that is very much in America's interest to encourage.

Yet shortly after the secretary of state's reported comments, the US undertook a series of unfriendly actions toward Cuba. The State Department spokesman denied that there was any specific proposal that Castro was considering for changing alliances. He stated that America would only consider improving relations with Cuba when Cuba no longer interfered in other countries' affairs.

In addition, in April 1982 the Reagan administration announced the reimposition of restrictions banning tourist and business travel to Cuba; these had been lifted during the Carter years. Finally, the US held a large-scale naval exercise in the Caribbean intended to show Cuba that the US could defend its interests in the region. As Wayne Smith (former head of the US Interests Section in Havana) disclosed, all these signs of a harder US policy toward Cuba took place after Cuban officials repeatedly expressed their desire to improve Cuban-American relations.

The Soviet Union, on the other hand, recently increased its aid to Cuba to the highest level it has ever provided. If Castro really is considering distancing himself from the USSR and drawing closer to the US, both American and Soviet foreign policies at present appear designed to discourage him from such a course of action.