Fidel Castro thanked Cubans for their well-wishes on his 90th birthday and criticised US President Barack Obama in a lengthy letter published in state media.
He appeared but did not speak at a gala in his honour broadcast on state television.
“I want to express my deepest gratitude for the shows of respect, greetings and praise that I’ve received in recent days, which give me strength to reciprocate with ideas that I will send to party militants and relevant organizations,” he wrote about his birthday on Saturday.
“Modern medical techniques have allowed me to scrutinise the universe,” wrote Castro, who stepped down as Cuba’s President 10 years ago after suffering a severe gastrointestinal illness.