In an open letter this week to U.S. bishops, Pope Francis called President Donald Trump’s mass deportation program a “major crisis."

U.S. border czar Tom Homan pushed back, saying the religious leader should leave border enforcement to his office and noted the Vatican is a city-state surrounded by fortress-like walls

Francis took the remarkable step of addressing the U.S. migrant crackdown in a letter to the bishops of the United States, who have criticized the expulsions as harming the most vulnerable. History's first Latin American pope has long made caring for migrants a priority of his pontificate,