HAVANA - Three men who served long US prison terms for spying have received a standing ovation in Cuba's parliament, as President Raul Castro declared that detente with Washington will not change the communist system he leads.

The last imprisoned members of the Cuban Five spy ring were freed this week in a sweeping deal that included the liberation of American contractor Alan Gross and a Cuban spy for the US from their jail cells in Cuba, and pledges to restore full diplomatic relations and loosen US restrictions on trade and travel to the island.

President Barack Obama said the changes are designed to encourage reform in Cuba's one-party system and centrally planned economy.

Mr Castro 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".

Mr Castro expressed gratitude to Mr 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.