But Castro on Saturday rejected that idea in his address to the twice-annual meeting of the National Assembly, saying "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."

The Cuban leader expressed gratitude to Obama for the "just decision" to release the men, who spied on anti-Castro exile groups in South Florida in the 1990s and have long been regarded as heroes in Cuba. Seated behind the three and their families was Elian Gonzalez, who as a child in 2000 found himself at the center of a bitter, high-profile custody battle between relatives in Miami and his father in Cuba.

In Florida on Saturday, Cuban-Americans gathhered to protest Washington's normalization of ties with Havana. Demonstrators chanted "Obama, traitor" at the event, which attracted around a couple hundred people as it got underway, according to the Associated Press.

Meanwhile in Havana, Raul Castro closed his speech with "Viva Fidel!" in reference to his older brother, who has not been seen nor heard from since Wednesday’s historic announcement, prompting fresh speculation about his health and whereabouts.

While Obama is clearing the way for limited exports to Cuba and freer travel for certain Americans, including academics and artists, Congressional action would be needed to end the decades-old embargo Cuba blames for the dire condition of its infrastructure and economy.

Castro reminded Cubans that the embargo remained in place, particularly limits on international financial transactions that Cuba accuses of blocking 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 also confirmed he would attend the Summit of Americas in Panama in April, where he is expected to have further discussions with Obama.

Al Jazeera and wire services