Fidel Castro has put a damper on hopes of improved U.S.-Cuba relations by rejecting the idea that the island should release political prisoners. The 82-year-old dictator claims that President Obama misinterpreted remarks made by his brother and successor, Raul, at the recent Summit of the Americas. “Affirming that the president of Cuba is ready to discuss any topic with the president of the United States expresses that he's not afraid to broach any subject,” Fidel wrote of his 77-year-old brother, adding that “It's a sign of bravery and confidence in the principles of the revolution.” He made it clear that “Nobody should assume that he was talking about pardoning those sentenced in March 2003.” He was referring to 54 leading political opposition leaders who remain imprisoned after a crackdown that led to the arrest of some 75 dissenters. Castro also criticized the U.S. President, whom he had previously praised, by accusing him of “superficiality.”