The Cuban government will free 52 political prisoners, Catholic officials in Havana said Wednesday, the largest release of captive dissidents in decades and a surprise gesture that could help thaw relations with the United States. The scheduled release of those arrested in a March 2003 crackdown against pro-democracy activists on the island was brokered by the country's archbishop, Cardinal Jaime Ortega, with help from visiting Spanish diplomats. Ortega met this week with Cuban President Raúl Castro, brother of the country's ailing dictator. Fidel Castro, 83, has not been seen in public for four years but remains the country's supreme leader and probably approved the move. The Cuban government had nothing to say about the release, and human rights activists were cautious in their response to the church's announcement. "This is significant, and good news, from the point of view of the prisoners and their families," Elizardo Sanchez, head of the Cuban Commission for Human Rights, said by telephone from Havana. "But it is a political decision of the Cuban government, taken for short-term political motives, to have an immediate effect overseas, not in Cuba itself."