The message came more than a decade ago, when Salvadoran President Mauricio Funes was a reporter for a Salvadoran television channel and interviewed convicted bomber Ernesto Cruz Leon in Havana.
"Funes was here in the year 2000 ... the only journalist from my country who was permitted to come, with the authorization of Fidel Castro," Cruz Leon told The Associated Press in an exclusive interview. "He brought me a message from President Fidel Castro himself that he was aware of my cooperation in clarifying these events, and that because of it the death penalty would not be applied, but all I had was his word."
It was not clear if Funes disclosed the message from Fidel as part of his report. A spokesman for the El Salvadoran president, David Rivas, had no immediate comment on Thursday.
Funes returned to Cuba in October 2010, this time as head of state, shortly after El Salvador restored diplomatic relations with the communist-run island.
In December, a Cuban court reduced the death sentences of Cruz Leon and another Salvadoran involved in the 1990s bombings, Otto Rene Rodriguez, to 30 years in jail. A Cuban-American convicted of killing a policeman in a separate case also had his death sentence vacated.
They had been the only three people remaining on Cuba's death row.
During the October visit, Funes told Cuban state-run media that the fate of the jailed Salvadorans was not on his agenda.
"One of the terrorists caused the death of an Italian citizen and put the Cuban people at risk," Funes told government Web site Cubadebate at the time. He said the men had confessed, "and we don't need to defend someone who has admitted to the crimes" that they committed.
The 1990s bombing campaign, which was designed to cripple Cuba's tourism industry, killed Italian national Fabio di Celmo and wounded about a dozen people.
Both Cruz Leon and Rodriguez said the court decision to reduce their sentences was not something they had requested.
Cruz Leon said that when Funes was elected in 2009, he remembered the interview and "hoped that in some way he would intercede on our behalf," but he did not know whether the Salvadoran leader played any role in getting the sentences reduced.
Cruz Leon and Rodriguez were interviewed by AP on Tuesday at a government house in a leafy residential area of Havana, with Cuban officials present. Both insisted that they were not pressured to do to the interview, and were not promised anything in return.
In the interview, Cruz Leon also provided details of his capture that had never before been publicly disclosed, saying that he always suspected another Salvadoran man involved in the attacks or someone working with him turned him in.
Cruz Leon said that the day after setting a bomb in Havana's Copacabana hotel - which killed di Celmo - he received a call from Francisco Chavez Abarca, the Salvadoran man who hired him for the job.
He said Chavez Abarca told him to go to another hotel, the Capri, to pick up an envelope filled with cash. Cruz Leon said he was against it, but agreed in the end when Chavez Abarca insisted.
"When I got there I asked the man at the information desk if someone had left me a package, and I could tell that he was nervous," Cruz Leon said. "From the corner of my eye I saw someone move in a guayabera" - a traditional Cuban dress shirt - "and that was that."
A moment later he was in custody.
Chavez Abarca, who was arrested in Venezuela last year and extradited to Cuba, has acknowledged his role in the bombings while in Cuban custody, and testified at his Cuban trial that he was working for a former CIA operative named Luis Posada Carriles.
Posada is currently on trial in El Paso, not for the bombing campaign directly, but for allegedly lying about his involvement in it and other militant activity during immigration hearings .
"I have always had my doubts" whether Chavez Abarca or someone else working for him told authorities to wait at the Capri, Cruz Leon said. "But I know for sure I was ratted out."
Associated Press reporter Andrea Rodriguez in Havana and Marcos Aleman in San Salvador contributed to this report.