Robert A. Maheu, a former Howard Hughes confidant and CIA operative once involved in a failed plot to poison Fidel Castro, has died in a Las Vegas hospital. He was 90.

Maheu died Monday evening of congestive heart failure at Desert Springs Hospital, according to his son, Peter Maheu.

Maheu was the public face of Hughes' massive corporate empire in the 1960s, a period in which the troubled aviator and one-time Hollywood playboy was increasingly reclusive and dogged by phobias. Hughes spent the later part of the decade holed up in his Las Vegas hotel suite, directing Maheu and his casino and development interests via memo.

Maheu worked for the FBI in the early 1950s and later as a private investigator who counted the CIA among his clients.

In 1960, Maheu was enlisted by the CIA to recruit a mobster for a "sensitive mission requiring gangster-type action," according to a recently released CIA dossier known as "the family jewels."

"Fidel Castro is the mission target," the document said.

Maheu approached reputed gangster Johnny Roselli and represented himself as an agent for international corporations wanting the Cuban leader dead, according to the document.

Roselli introduced Maheu to two wanted mobsters, Momo Giancana, Al Capone's successor in Chicago, and Santos Trafficante. The CIA gave them six poison pills, and they tried unsuccessfully for several months to have several people put them in the Castro's food.

The plot was dropped after the failed CIA-sponsored Bay of Pigs invasion of Cuba, the document said.