( CNN ) -- Juanita Castro , the younger sister of Cuban leaders Fidel and Raul Castro , worked for the CIA during some crucial years of the Cold War , she says in her new memoir . Juanita Castro , originally a supporter of the Cuban revolution that brought Fidel Castro to power in 1959 , said she became disillusioned by growing injustice . `` They wanted to talk to me because they had interesting things to tell me , and interesting things to ask of me , such as if I was willing to take that risk , if I was ready to listen to them . I was semi-shocked , but I said yes anyway , '' she told CNN affiliate Univision-Noticias 23 in Miami , Florida . Univision 's interviewer , journalist Maria Antonieta Collins , co-wrote the book . `` My Brothers Fidel and Raul , the Secret History '' was released Monday . In the book , Juanita Castro said she was introduced to the world of the CIA through a close friend on the island nation , Virginia Leitao da Cunha , wife of the Brazilian ambassador to Cuba in the early 1960s . In June 1961 , under the guise of visiting her sister Enma in Mexico City , Castro met a CIA agent who called himself `` Enrique , '' the memoir says . In those first meetings in Mexico , which took place shortly after the failed Bay of Pigs invasion , Enrique asked the young woman about general information regarding Cuba since the revolution , and then asked whether she would work for the agency , according to the book . The job that Enrique described was to help protect CIA agents working in Cuba , Castro said . `` The CIA has people in Cuba . Some could be discovered or already have . The mission is to protect them and move them from one place to another , providing the most security possible , '' the agent told her , according to the book . The CIA declined to comment on the book 's claims . Her first mission was to deliver documents , money and messages hidden in canned goods from Mexico to Cuba , according to the book . Castro wrote that she agreed to help on the condition that she would not do anything violent against her brothers . She also refused payment when it was offered , she said . The CIA communicated through a short-wave radio . At an appointed hour daily , if the waltz `` Fascination '' aired on the radio , Castro would know that a message would follow . An overture from `` Madame Butterfly '' meant that no message was coming , according to the book . A special code was made up of numbers , which Castro would decode with a manual , she wrote . The period of her cooperation , from 1961 to 1969 , included the Cuban Missile Crisis , which changed the way the Cold War was being waged . To resolve the crisis , the Soviet Union agreed to dismantle the missiles it had placed in Cuba in exchange for assurances that the United States would not invade Cuba . In 1964 , Castro decided to leave Cuba for good , becoming an exile in Miami . She worked with anti-Castro exile groups there , and continued to cooperate with the CIA , according to the book . The relationship ended when U.S. policy toward the Soviet Union changed during Richard Nixon 's presidency . As tensions eased with the Soviet Union , the United States would no longer back anti-Castro exiles , two CIA agents told her . When they asked her to use her influence to downplay rhetoric of a communist threat , she quit . The Cuban government had no immediate response to the publication of the book , Jorge Bolanos , chief of the Cuban Interest Section in Washington , told CNN en Español on Monday . `` I have n't received any reaction from the Cuban government , '' he said . `` I am not in the position to comment about a book which I have not read yet . '' CNN 's Mariano Castillo and Carol Cratty contributed to this report .
Interview by Fidel Castro 's daughter , Juanita , says she worked for CIA . Communicated via coded messages on short - wave radio . worked with CIA between 1961 and 1969 ; left Cuba in 1969 for Miami . agreed to help on condition she did not do anything violent against her brothers .