Donald Trump went on the defense after Pope Francis suggested the Republican presidential front-runner "is not Christian" because of his anti-immigrant proposals and rhetoric.

Pope Criticizes Trump On Immigration

On Wednesday, the Pope criticized Trump over his harsh policy on immigration reform, which includes building a wall along the U.S.-Mexico border.

"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian," Francis told reporters when asked about Trump's campaign. "This is not in the gospel."

When asked by a reporter if an American Catholic should vote for the billionaire businessman, the pontiff said he would not give advice.

"I am not going to get involved in that. I say only that this man is not Christian if he says things like that," he said. He then referred to Trump directly, saying, "We must see if he said things in that way and in this I give the benefit of the doubt."

Trump Fires Back

In response, Trump fired back at a campaign rally in South Carolina on Thursday, telling his supporters the Pope "said negative things about me because the Mexican government convinced him that Trump is not a good guy. He actually said that maybe I'm not a good Christian or something. It's unbelievable." Trump added that it "is really not a nice thing to say."

Trump, who has also vowed to deport millions of undocumented immigrants living in the U.S. if he wins the White House, also released a statement, saying that the Islamic State would love to have the Vatican as its "ultimate trophy."

"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 because this would not have happened," reads the statement.

Trump Says He's Proud of His Faith

The real estate mogul also said it is "disgraceful" for the leader of the Roman Catholic Church to question his faith.

"I am proud to be a Christian and as President I will not allow Christianity to be consistently attacked and weakened, unlike what is happening now, with our current President. No leader, especially a religious leader, should have the right to question another man's religion or faith," Trump said.

At another point in the statement, Trump suggested that the Mexican government was "using the Pope as a pawn."

Later on Thursday, Trump's social media director and senior adviser Dan Scavino argued that Francis was being hypocritical, since the Vatican is surrounded by protective walls.

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