HAVANA, Cuba (CNN)  -- President Obama misinterpreted Cuban President Raúl Castro's offer to start talks with the United States, Castro's brother Fidel said Wednesday, appearing to dismiss the U.S. leader's call for Cuba to release political prisoners.



Fidel Castro appears with Venezuela's Hugo Chavez, left, and brother Raúl Castro in a photo released in June.



In an essay published in state-run newspapers Wednesday, the ailing revolutionary leader said the people Washington calls political prisoners are "in the service of a foreign power that threatens and blockades our homeland."



Fidel Castro's comments come after signs of a thaw in the decades-old impasse between the United States and the communist-ruled island to its south.



Obama lifted all restrictions on visits and money transfers between American citizens and relatives in Cuba this month, while Raúl Castro said Cuba is prepared to talk with the United States about "everything -- human rights, freedom of the press, political prisoners."



Speaking at a conference of inter-American and Caribbean leaders Sunday, Obama said the Cuban leader's declaration was "a sign of progress."



He added that the Cuban government could send a much clearer, more positive signal by releasing political prisoners or reducing fees charged on remittances Americans send to relatives in the country.



But Fidel Castro wrote Wednesday, "There is no doubt that the president misinterpreted Raúl's statements."



"When the president of Cuba said he was ready to discuss any topic with the U.S. president, he meant he was not afraid of addressing any issue," Castro wrote. "That shows his courage and confidence on the principles of the revolution."



He said Cuba would be willing to release prisoners held since a 2003 crackdown on dissidents if the United States would release five Cubans convicted of spying in 2001.



And he criticized Obama for not doing more to lift the U.S. embargo on Cuba, imposed in 1962.



"Should we wait for so many years before his blockade is lifted?" Castro asked. "He did not invent it, but he embraced it just as much as the previous 10 U.S. presidents did."



Castro ceded power to his brother in 2006 before undergoing surgery for a still-undisclosed intestinal condition. But he remains head of the Communist Party, and his essay raises the question of who would be calling the shots in any talks with Washington.



"Who's in charge?" one Havana man asked Wednesday. "Raul -- ah, Fidel -- ah, Raúl."



But a woman who spoke to CNN said, "The president is Raúl. He's the one you have to listen to now."
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