HAVANA - Cuban President Raul Castro sent a stark message to Washington on Saturday as the White House works to reverse a half-century of hostility between the U.S. and Cuba: Don't expect detente to do away with the communist system.

Castro's speech to Cuba's National Assembly was a sharp counterpoint to the message President Obama gave in his year-end news conference the day before. Obama reiterated that by engaging directly with the Cuban people, Americans were more likely to encourage changes to Cuba's one-party system and centrally planned economy.

"We must not expect that in order for relations with the United States to improve, Cuba will abandon the ideas that it has struggled for," Castro said.

Also appearing before parliament, shaking their fists in victory, were three convicted spies just released from long U.S. prison terms. The last imprisoned members of the "Cuban Five" spy ring were freed last week in a sweeping deal that included American contractor Alan Gross and a Cuban who had spied for the U.S., both released from their cells in Cuba as a first step toward the restoration of full diplomatic ties and a loosening of U.S. trade and travel restrictions.

While the 83-year-old Castro spoke in Havana, other Cubans of his generation were leading a protest in Miami against plans to normalize relations with the Castro government. About 200 people showed up, most of them older Cuban exiles.

"The Cuban resistance will continue both on the island and in exile to do everything and continue the struggle until Cuba is truly free and democratic once again," said Sylvia Iriondo, an activist with Mothers Against Repression.

Castro also expressed gratitude to Obama during his speech, calling it a "just decision" to release the men who spied on anti-Castro exile groups in South Florida in the 1990s and who have long been regarded as heroes in Cuba. Seated behind the three and their families was Elian Gonzalez, the young Cuban rafter at the center of a bitter custody battle in 2000 between relatives in Miami and his father in Cuba.

The president closed with a shout of "Viva Fidel!" in reference to his older brother, who has not been seen or heard from since the historic development was announced on Wednesday, provoking speculation about his health and whereabouts.

The executive orders Obama announced Wednesday can clear the way for limited exports to Cuba and freer travel by specific categories of Americans such as academics and artists, but he acknowledged his need to work with Congress to end the decades-old embargo Cuba blames for the dire condition of its infrastructure and economy.

Castro reminded Cubans the embargo remains in effect, particularly limits on international financial transactions that Cuba says block its access to credit and international investment.

"An important step has been taken, but the essential thing remains, the end of the economic, commercial, and financial blockade against Cuba, which has grown in recent years, particularly in terms of financial transactions," he said.

Castro confirmed he would attend the Summit of Americas in Panama in April, where he is expected to have further discussions with Obama.

Late Friday, Cuban state television showed four of the Cuban Five celebrating together.