Pope Francis questioned the Christian faith of Republican presidential hopeful Donald Trump Thursday while criticizing his stance on immigration.
Speaking with reporters on a flight to Vatican City at the end of a five-day visit to Mexico, Francis said in a reference to Trump that "a person who thinks only about building walls…and not building bridges, is not a Christian."
"Vote, don't vote, I won't meddle. But I simply say, if he says these things, this man is not a Christian," Francis said in a response to a question about Trump's anti-immigration stance.
Trump has pledged to build a wall between the US and Mexico, deport millions of undocumented immigrants and to keep out Muslim immigrants if elected president.
Not one to turn the other cheek, Trump fired back on Facebook: "No leader, especially a religious leader, should have the right to question another man's religion or faith," he wrote. "I am proud to be a Christian and as president I will not allow Christianity to be consistently attacked and weakened."
Trump added that in the hypothetical case of an attack on the Vatican by Islamic State (ISIS), Francis would have wanted him to be president.
"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," Trump said. "ISIS would have been eradicated unlike what is happening now with our all talk, no action politicians."
Trump has been the Republican frontrunner in the race for the presidential nomination but a national poll Thursday showed Senator Ted Cruz beating him out for the lead, for the first time.