Wednesday, February 24, 1999; Page A20

A POLITICAL leader with the interests of his hard-pressed population at heart would have made the most of President Clinton's recent extension of humanitarian, personal and cultural contacts with the Cuban people. But not the Communist dictator Fidel Castro. Instead of permitting citizens modest relief, he tightened the existing restrictions on contacts with the United States. Given a fresh choice in alternate post-Cold War circumstances between improving the lot of his people and protecting his power, he has again chosen the Stalinist way.

The Clinton offer of January included small steps designed to wiggle between an easing of the lonely, longstanding American embargo on trade and investment and a stiffening. The American political debate unfortunately leaves little room for more. Still, the visit to Cuba by Pope John Paul II a year earlier had kindled hopes that Fidel Castro was now inclined to extend certain personal liberties and contacts. It seemed possible that Mr. Castro could live with these initiatives without being paralyzed by the thought of losing power.

The hopes were misguided. Mr. Clinton made a gesture of acknowledgment of the pope's criticism of the embargo as unjust. Fidel Castro responded by enacting a "Law for the Protection of Cuba's National Independence and Economy." It threatens penalties of 10 or 20 years for any Cuban citizen who in the regime's eyes lends himself to the "subversive" proposals of the United States. This is how Fidel Castro means to handle the brave and small but seemingly irreducible number of dissidents, including independent journalists who do our calling proud.

At face it is strange that Mr. Castro should think the contact proposals could contribute to his overthrow. This is a man who by combining police rule and Cuban nationalism has endured -- to him his greatest triumph -- everything the United States could throw against him in nearly 40 years. But having survived an invasion and many assassination plots, he may wonder whether he can also survive the belated American effort to help construct a civil society of non-Communist social and interest groups. Fidel Castro may know better than anyone what his vulnerabilities are.