The Pope has questioned US Republican presidential candidate Donald Trump’s Christianity over his call to build a border wall with Mexico.
Pope Francis said “a person who thinks only about building walls… and not of building bridges, is not Christian”.
The New York businessman supports deporting nearly 11 million undocumented immigrants.
Calling himself a “proud Christian”, Mr Trump blamed Mexico for the Pope’s remarks, calling them “disgraceful”.
Mr Trump has alleged that Mexico sends “rapists” and criminals to the US.
Pope Francis made the comments at the end of a trip to Mexico.
“A person who thinks only about building walls, wherever they may be, and not of building bridges, is not Christian. This is not the gospel,” he said.
He declined to say whether Americans should vote for Mr Trump, who is leading the Republican race for president.
“I say only that this man is not Christian if he has said things like that. We must see if he said things in that way and I will give him the benefit of the doubt,” the Pope said.
The Pope also said in response to a question about whether contraception could be used to prevent Zika virus that for some cases the “lesser of two evils” can be used. He said abortion “is a crime, an absolute evil,” but that avoiding pregnancy is not.
Addressing a rally in South Carolina, Mr Trump responded to the Pope’s comments.
“For a religious leader to question a person’s faith is disgraceful. I am proud to be a Christian,” Mr Trump said. “No leader, especially a religious leader, should have the right to question another man’s religion or faith.”
“[The pope] said negative things about me. Because the Mexican government convinced him that Trump is not a good guy,” he said.
He also said the Vatican is the so-called Islamic State’s “ultimate trophy”, and “if and when” the group attacks it “the Pope would have only wished and prayed that Donald Trump would have been President because this would not have happened.”
Jerry Falwell Jr, the president of conservative Christian Liberty University and a Trump supporter, told CNN the Pope went too far,
“Jesus never intended to give instructions to political leaders on how to run a country,” he said.
Send news and suggestions to firstname.lastname@example.org