Cuban President Raul Castro paid a call Sunday on Pope Francis at the Vatican to thank him for working for Cuban-U.S. detente—and said he was so impressed by the pontiff he is considering a return to the Catholic church’s fold.

“Bienvenido (welcome)!” Francis said in his native Spanish, welcoming Castro to his studio near the Vatican public audience hall. The Cuban president, bowing his head, gripped Francis’ hand with both of his, and the two men began private talks. The meeting lasted nearly an hour, as the Argentine-born Francis and Castro spoke in Spanish.