HAVANA (AP) -- Fidel Castro mocked President Barack Obama on Thursday for saying he’s open to changing U.S. policy toward Cuba if there is change on the island first, calling the U.S. leader “stupid.”

Writing in one of his semiregular essays published across state-run media, Castro reacted with sarcasm to reported comments that Obama would be open to a different relationship with Cuba when there is political and social change.

“How kind! How intelligent!” Castro said. “Such kindness still has not allowed him to understand that 50 years of blockade and crimes against our country have not been able to bow our people.”

Cuba uses the term “blockade” to refer to the nearly five-decades-old economic embargo against the island.

“Many things will change in Cuba, but they will change through our efforts and in spite of the United States. Perhaps that empire will fall first,” Castro added, a reference to the United States.

Castro wrote glowingly about Obama when he was elected in 2008, saying, “The intelligent and noble face of the first black president of the United States since its founding two and one-third centuries ago as an independent republic had transformed itself under the inspiration of Abraham Lincoln and Martin Luther King into a living symbol of the American dream.”

But Castro has increasingly shown disillusionment as Cuban-U.S. relations remain in a deep freeze, despite measures undertaken by Obama allowing more remittances and travel to the island.

Castro also criticized as “brutal, blundering and expected” a U.S. judge’s recent ruling that an imprisoned Cuban intelligence officers must serve his parole in the United States instead of returning to his family on the island after he is released in early October.

The case of Rene Gonzalez, who holds dual American and Cuban citizenship, and four other agents imprisoned for espionage in the U.S. is one of the Cuban government‘s chief complaints about Washington, and newspapers and airwaves on the island call each day for their release.

“This is how the empire responds to the increasing demand around the world for their freedom,” Castro wrote. “If it weren’t so, the empire would cease to be an empire and Obama would cease to be stupid.”

Gonzalez and the others, collectively known as the “Cuban Five,” were convicted in 2001 of attempting to infiltrate U.S. military installations in South Florida. They also monitored militant anti-Castro groups and tried to place operatives inside the campaigns of anti-Castro politicians.

One of the five was convicted of murder conspiracy related to the 1996 shootdown by Cuban fighter jets of planes flown by an exile group.

Havana lauds the men as heroes. It contends that they were no threat to the U.S. government and were unfairly tried and given exorbitant sentences not commensurate with their activities.