The Pope said Trump's plan to build a wall on the Mexican border is "not Christian."
Donald Trump apparently will argue with anyone, even the Pope.
The outlandish GOP presidential hopeful called the Roman Catholic leader "disgraceful" after Pope Francis called Trump's comments about Mexicans "not Christian."
The Pope was returning to Italy from a highly popular visit to Mexico, where he addressed thousands of worshippers, and spoke to reporters on his plane.
Read: They Crossed the Line! Pope Francis Gets Angry with Crowd in Mexico For Making Him Fall
"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian," the Pope told journalists who asked him about Trump's controversial remarks about building a massive wall on the Mexican-U.S. border.
"This is not in the gospel," the Pope said.
Trump immediately fired back Thursday, posting a statement on his Twitter and Facebook campaign accounts.
"No leader, especially a religious leader, should have to question another man's religion or faith," the billionaire said.
"For a religious leader to question a person’s faith is disgraceful," Trump added.
"If and when the Vatican is attacked by ISIS, which as everyone knows is ISIS's ultimate trophy, I can promise you that the Pope would have only wished and prayed that Donald Trump would have been president," he said.
Read: Pope Laughs at Baby Dressed Like Him, Tells Mother: 'You Have a Great Sense of Humor'
The Pope also made light of Trump's accusation that the religious leader was a pawn of the Mexican government.
"Thank God he said I was a politician because Aristotle defined the human person as 'animal politicus,''' the Pope said.
"So at least I am a human person," he said. "As to whether I am a pawn, well, maybe, I don't know. I'll leave that up to your judgment and that of the people," CNN reported.
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