Ailing Cuban leader Fidel Castro demanded on Thursday that US President Barack Obama return the US naval base at Guantanamo to Cuba without conditions, and he accused the new US leader of supporting "Israeli genocide" against Palestinians.

Castro, who had recently praised Obama as "honest" and "noble", lashed out at his administration for stating that Washington will not return Guantanamo if it has any military use for the US and without concessions in return.

"Maintaining a military base in Cuba against the will of the people violates the most elemental principles of international law," Castro wrote in a column posted on the government-run website www.cubadebate.cu.