A Cuban intelligence agent who spent more than 15 years in a United States prison says he's optimistic that softening U.S. attitudes will lead to the liberation of three fellow agents who remain behind bars.

Fernando Gonzalez, whom the Cuban government lauds as a national hero, told The Associated Press that one of the most positive signs he's seen is former Secretary of State Hillary Clinton's statement in a recent book that she recommended that President Barack Obama end the decades-long U.S. embargo on Cuba.

The case of the so-called Cuban Five has been linked to that of Alan Gross, a U.S. government subcontractor serving a 15-year prison sentence for bringing in sensitive technology.

Gonzalez says "at this moment there's a political context that makes me cautiously optimistic."