Fidel Castro: charming, extraordinarily smart, a great politician who knows his history. The assessment comes not from a communist comrade of the Cuban dictator but from a U.S. Marine general who retired last year as commander of America's Atlantic forces.

Not surprisingly, Gen. John Sheehan's dovish ideas about Cuba and its authoritarian leader have made Sheehan an object of ridicule from anti-Castro circles in Miami.After a military career spent trying to keep Marxist-Leninists like Castro at bay, Sheehan now supports legislation to end U.S. restrictions on sale of food and medicines to Cuba. He also sees Cuba as a military weakling compared with the era when Soviet arms deliveries to the island ran into the thousands of tons annually.

Once a frequent visitor to the U.S. naval enclave at Guantanamo Bay, Sheehan made his first visit last month to the real Cuba. He spent 81/2 hours with Castro and a day and a half with his brother Raul, Cuba's defense minister. Sheehan discussed his experiences in a telephone interview from his Virginia home.

"What do you think, we are stupid?" Fidel Castro responded incredulously to Sheehan's queries whether Cuba produces chemical or biological weapons.

"We don't want to give the U.S. a pretext for an attack," Sheehan quoted Castro as saying.

The status of Cuba's military has come under increasing debate late-ly in Washington as the Pentagon puts finishing touches on a comprehensive report about it. Accounts of the report leaked to The Miami Herald suggest the Pentagon believes Cuba poses no significant threat to the United States, partly because of the country's prolonged economic crisis.

Among the most outspoken critics is Rep. Lincoln Diaz-Balart, R-Fla., who in a recent speech accused Cuba of participating in narcotics trafficking and the Clinton administration of ignoring it. He also said Russia has been monitoring American military activities from an electronic espionage facility in Cuba.

Diaz-Balart added: "Under the guise of genetic, biological and pharmaceutical research, Castro is developing a serious germ and chemical warfare capability."

When Sheehan was in Cuba, Castro invited him to investigate the country's biotechnology operations. "You pick the buildings," Castro told his visitor, mindful that Sheehan had considerable information on the subject based on his prior duties as a Cuba-watcher for the Pentagon.

Sheehan said eight buildings were devoted to biotechnology. In one he visited, he said, technicians were trying to develop an AIDS vaccine.

Sheehan has long been regarded as an unconventional thinker. Some colleagues believe his penchant for innovation cost him a shot at becoming chairman of the Joint Chiefs of Staff.

One of those is retired Adm. Leon "Bud" Edney, former commander-in-chief of the U.S. Atlantic command and supreme allied commander in Europe, who praises Sheehan for creative ideas for coping with new realities of the post-Cold War but figures they were too radical for conservative military minds.