Pope Francis urged US President Barack Obama and Cuba's Raul Castro to continue building their nations' nascent reconciliation as he arrived in Havana Saturday at the start of a tour that will also take him to the United States.

"For some months now, we have witnessed an event which fills us with hope: the process of normalizing relations between two peoples following years of estrangement," he said.

"I urge political leaders to persevere on this path and to develop all its potentialities... as an example of reconciliation for the entire world."