Juanita Castro, sister of Cuban rulers Fidel and Raúl Castro, cooperated with the CIA in the 1960s -- a time when the U.S. agency was plotting to assassinate Fidel and overthrow his revolution -- according to an exclusive Univisión-Noticias 23 report on her newly published book.

The report also revealed that Juanita, who broke with her brothers' revolution in 1964, hid government opponents in her home; that Fidel refused to visit her because the house was ``surrounded by worms;'' and that their mother often intervened with Raúl to help Castro critics, jailed or fugitive.

Described as the Castro family's best-kept secret in the weeks that preceded the release of her book Monday, Juanita's revelation of her link with the CIA came as a short teaser at the end of a Univisión-Noticias 23 report on the book broadcast at 11 p.m. Sunday.