Republican presidential front-runner Donald Trump has a message for Pope Francis: Stay in your lane.

Trump called out the pope during a recent Fox Business Network interview, saying the pontiff didn’t fully comprehend the immigration challenges between the U.S. and Mexico.

“So I think the pope is a very political person and I think that he doesn’t understand the problems our country has,” Trump said.

Trump added he didn’t think the pope “understands the danger of the open border we have with Mexico.”

He added, “And I think Mexico got him to do it because Mexico wants to keep the border just the way it is because they’re making a fortune and we’re losing.”

Trump has vowed for months to build a wall along the border with Mexico – and make Mexico pay for it. All along, he's made combating illegal immigration a centerpiece of his presidential campaign, claiming credit for kickstarting the debate which now features heavily in the GOP primary race.

But the pope has gently, but clearly, weighed in on the immigration debate in America, and the heated rhetoric on the issue.

In his address to Congress last September, Pope Francis urged lawmakers not to be “fearful of foreigners” and reminded them that many are “descended from immigrants.”

Pope Francis heads to Mexico Friday for a one-week trip.

Among other things, the pontiff, the child of immigrants himself, is expected to address Mexico’s immigration problem.