Pope: Only building border walls 'not Christian'

ABOARD THE PAPAL PLANE -- Thrusting himself into the heated American presidential campaign, Pope Francis declared Thursday that Donald Trump is "not Christian" if he wants to address illegal immigration only by building a wall along the U.S.-Mexico border.

Trump fired back, saying it was "disgraceful" for a religious leader to question a person's faith.

Francis' comments came hours after he concluded a visit to Mexico, where he prayed at the border for people who died trying to reach the U.S. On the papal plane, he was asked what he thought of Trump's pledge to build a wall along the entire length of the border and expel millions of people in the U.S. illegally.

"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian," he said. Francis said he would "give the benefit of the doubt" because he had not heard Trump's border plans independently but added, "I say only that this man is not a Christian if he has said things like that."