(AP) - Donald Trump says a religious leader questioning a person's faith is "disgraceful," responding forcefully to comments from Pope Francis that anyone who wants to build a border wall isn't a Christian.

The Republican candidate for president says Thursday the Pope should wish that he is elected to the White House, and he accused the Mexican government of using Francis as a "pawn" and says the leader of the Roman Catholic Church "only heard one side of the story."

Pope Francis spoke as he traveled home from a visit to Mexico. When asked about Trump's promise to build a wall along the U.S.-Mexican border, Francis said: "A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian."

Trump replied to the Pope during a campaign stop in Kiawah Island, South Carolina. He says, "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."

Trump went on to say, "for religious leader to question a person's faith is disgraceful."

"No leader, especially a religious leader, should have the right to question another man's religion or faith," Trump says.

When asked about Donald Trump's views on immigration, Pope Francis says anyone who wants to build a wall along the U.S.-Mexican border isn't Christian.

Trump has promised to build a wall along the Mexican border from Texas to California and expel 11 million people who are in the country illegally if elected president. The Pope's comments en route home from Mexico came hours after he prayed at the Mexico-U.S. border for migrants who died trying to reach the United States.

"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian," Francis said. "This is not in the Gospel."

Not having heard Trump's border plans independently, Francis said he'd "give him the benefit of the doubt." But he added:

"I'd just say that this man is not Christian if he said it this way," Francis said.