It's tempting to think that Mikhail Gorbachev's visit to Cuba this week signals a major shift in Moscow's relationship with Havana. Certainly the Bush administration, is hopeful that Gorbachev will break new ground.

There is even speculation in some quarters that the Soviet leader is planning another dramatic announcement, something in keeping with the "new thinking" that has produced peace agreements in Afghanistan and Angola and unilateral reductions in conventional forces in Europe.Where Gorbachev is involved, virtually anything is possible. But the chances of a dramatic departure in Soviet-Cuban relations are very remote.

A more likely outcome is a public reaffirmation of the Soviet-Cuban special relationship and a private understanding that Cuba will try to gain access to American dollars to solve its hard currency shortage. Washington should resist this strategy.

Clearly, Cuba is a heavy economic burden for the Soviet Union, receiving aid of about $4.5 billion a year. This represents 50 percent of all Soviet assistance to the Third World and makes Cuba the single largest recipient of such aid.

Considering the Soviet Union's much discussed economic problems, Moscow's aid to Havana would seem a likely place to begin belt-tightening. But don't expect this to happen.

Cuba is a vital Soviet outpost and ideological ally in the U.S. sphere of influence. Cuba also advances Soviet interests in the Third World by engaging in behavior that would be unacceptable for a superpower. It gives military support to Marxist guerrilla groups and helps consolidate and protect Marxist governments.

Still, Gorbachev is serious about reducing the costs of the Soviet empire. Naturally, he would like to do this without giving up the military and strategic benefits of Moscow's relationship with Havana.

There are two ways to achieve this: Make the inefficient Cuban economy more productive, or persuade the United States to lift its economic embargo of Cuba.

An increase in Cuba's productivity is unlikely, as long as Fidel Castro maintains total control of the economy.

He allowed a measure of guided free enterprise to reduce popular discontent and revive the economy in the early 1980s. But Castro felt extremely threatened by the success of the reforms.

This explains his launching of the so-called rectification campaign in 1986, which increased economic centralization and replaced material incentives with "moral" ones. The policy is making Cuba's bad economic situation worse.

But Gorbachev will not press Castro on economic matters. He probably shares Castro's fear that reforms could unleash forces within the unhappy Cuban population that might threaten political stability.

The option of re-establishing economic relations between Cuba and the United States is, therefore, much more attractive to the Soviet Union. It is also better for Castro.

Washington must not play into Havana's hands. Castro needs relations with the United States much more than Washington needs relations with Havana.

By giving him premature access to the hard currency he desperately needs, the United States would allow him to postpone indefinitely an economic and political opening in Cuba.

The United States should be disposed toward a more normal relationship with Cuba, and should continue to negotiate matters of mutual concern. But a lifting of the economic embargo should follow, not precede, a Cuban glasnost and perestroika.