Cuban President Raul Castro spent Sunday in private meetings with socialist ally Hugo Chavez after publicly thanking the Venezuelan president for helping Cuba through difficult times. Castro - on his first trip abroad since becoming Cuba's president - was not scheduled to appear in public the day after he and Chavez agreed to joint projects worth more than $2 billion. Chavez, a longtime ally of Fidel Castro, gave Fidel's younger brother a warm welcome to Venezuela on Saturday, praising him for challenging US "imperialism" for decades. Castro, in turn, thanked Venezuela for increasing cooperation with the communist-led island.