Nearly two decades of animosity between the United States and Cuba have left a majority of Americans with an unfavorable view of the revolutionary Caribbean island. But 59 per cent of those polled favor re-establishing normal relations with Fidel Castro's government, according to a study by Potomac Associates, the Washington-based research group.

The study, based in part on a national public opinion survey conducted in mid-April by the Gallup Organization, shows that a slim majority (51 per cent) perceives Cuba as a threat to U.S. security, and that half of them believe Castro has been trying to stir revolutionary activity throughout Latin America.

Those polled overwhelmingly favored normalizing relations with Castro's Cuba only under terms heavily favorable to U.S. interests.

The study showed 52 per cent opposed to partially lifting the U.S. embargo before re-establishing diplomatic relations, and 59 per cent rejecting Cuban claims for damages suffered by the embargo or the Bay of Pigs invasion.

Moreover, Americans want Cuba to cut back its military forces in Africa (46 to 35 per cent), and to release American prisoners from Cuban jails (62 to 23 per cent).

The authors of the report, entitled "The United States and Cuba: Old Issues and New Directions," are William Watts, President of Potomac Associates, and Jorge I. Dominguez, Harvard University professor of government, who was born in Cuba.

"Achievement of broad American support for any genuine rapprochment will require carefully timed conciliatory steps and concessions from Cuba as well as the United States," the author said.

The Cuban concessions, they suggested, would provide President Carter with political leverage at home to offset opposition to U.S. concessions.

"Neither side can expect to achieve its objectives fully, but stand to gain in some areas - including terrorism and hijacking as well as matters like trade and various scientific, cultural and other exchanges - while they yield in others," Watts and Dominguez asserted.