New York (CNN) -- The convicted architect of a plot to blow up jet-fuel supply tanks and a pipeline at New York City's John F. Kennedy International Airport is suspected of having conspired to murder one of his attorneys, among others, while in jail, according to a letter unsealed in Brooklyn federal court.
Russell Defreitas allegedly asked his fellow prisoners to help him carry out several murders, according to a March 2010 letter from prosecutors to Defreitas' attorneys, which was released Tuesday.
He allegedly told a fellow inmate that he wanted his attorney, Mildred Whalen, whom he described as "Jewish," dead "because she is the reason his first attorney was removed from the case."
Whalen told CNN that she thought the claims were "ridiculous" and that she never felt threatened by Defreitas.
The letter says Defreitas also threatened to kill a witness named "Rutherford," as well as an unnamed prosecutor. According to the inmate, who is identified in the letter as "W1," Defreitas said that his co-defendant in the JFK plot, Abdel Nur, told him that the prosecutor "had to go."
Defreitas asked the inmate to contact his wife in Guyana and to deliver these messages to her, in exchange for a "promotion in Muslim ranks" and access to Defreitas' "contacts," the letter says.
Another target of Defreitas' alleged prison plot included Steve Francis, an informant who secretly taped Defreitas and his JFK plot conspirators.
He allegedly discussed plans to kill Francis with a second prisoner, identified in the letter as "W2."
Defreitas told the prisoner that he thought Francis had taped around 150 hours of recordings regarding the JFK plot, but had recently found out that there were more than 300 hours, the letter detailed.
He allegedly told the prisoner that "the only way to beat the case now was to have Francis killed," according to the letter. The prisoner apparently would have been paid by Defreitas' associate, Harry Baptiste, in exchange for murdering Francis.
Defreitas' former attorney, Whalen, said the allegations were unsubstantiated, which is why they were not admitted during trial.
Defreitas, a U.S. citizen from Guyana, was sentenced to life in prison last year for masterminding the airport plot.
CNN's Jonathan Noah contributed to this report