Pope Francis on Tuesday reprimanded Donald Trump for starting to carry out mass deportation plans, warning the treatment of migrants "will end badly."

In a letter to American bishops, Francis leveled unusually direct criticism at the administration on an issue he has made central to his papacy.

In the letter, the pope said the criminalization of migrants and the mass deportations planned by the U.S. government are dangerous and called the country's current immigration policies a “major crisis.