Ailing Cuban leader Fidel Castro, who has not been seen in public for 16 months, suggested on Monday he might give up his formal leadership posts - the first time he has spoken of his possible retirement since he fell ill.

"My elemental duty is not to hold on to positions and less to obstruct the path of younger people," the 81-year-old Castro said in a letter read on Cuban state television.

Castro, who took power in a 1959 revolution, handed over temporarily to his brother Raul Castro in July 2006 after undergoing stomach surgery for an undisclosed illness.