WASHINGTON - President Barack Obama hailed him as one of the best spies America has ever had in Cuba, but precious little is known about the Cuban man freed in a prisoner swap on Wednesday after two decades of incarceration on the Communist island.
The US government did not identify the man but credited him for providing information that helped authorities root out a network of spies working for Cuba in the United States, including two senior US government officials.
He was exchanged for three Cuban intelligence agents held in the United States.
The spy swap came during a US policy shift that saw Obama pledge to restore diplomatic relations with Cuba more than 50 years after the United States severed them. "Cuba today released one of the most important intelligence agents that the United States has ever had in Cuba," Obama declared in a televised address, which more broadly announced a big shift in policy after decades of hostility.
Obama said his sacrifice, until Wednesday, had "been known to only a few."
US officials did not spell out when the spy in Cuba provided material that led to subsequent US arrests or give details about what information he provided.
The US Director of National Intelligence's office said information he gave helped US investigators identify and convict Ana Belen Montes, a senior Defence Intelligence Agency official who was one of the highest-ranking US officials ever proven to have spied for Cuba.
Montes was a senior intelligence analyst at DIA when she was arrested by the FBI in September 2001. In March the next year, she pleaded guilty to conspiracy to commit espionage on behalf of Cuba and is serving a 25-year sentence.
A US official said that Montes, while at the DIA, disclosed identities of US intelligence officers and gave other classified information to the Cuban Intelligence Service.
Information provided by the unnamed Cuban also helped the United States identify a State Department official who, with his wife, had spied for Cuba for nearly three decades before being arrested by the FBI in 2009.
Walter Kendall Myers is serving a life sentence without the possibility of parole, while his wife, Gwendolyn Myers, is serving a seven-year prison sentence.
The Cuban informant also provided information that helped identify a Florida-based cell of five Cuban spies, who sought to infiltrate U.S-based anti-Castro groups as well as the US military's Southern Command. They were arrested in 1998.
Three of the Cuban spies arrested were freed as part of the prisoner swap on Wednesday, the US official said.