Republican presidential candidate Donald Trump is mocking the brief meeting Bernie Sanders had with Pope Francis Friday, which the GOP front-runner said was a short "five minutes."

"You know, he went to see the pope," Trump said of Sanders during a rally in Syracuse, New York Saturday. "Five minutes. Then he came out. He said, 'We talked about the environment, we talked about global warming, we talked about all these different things.'"

"And I said, wait a minute, he was only there five minutes," Trump added. "So the pope gave him five minutes. I wonder why the pope gave him five -- he shouldn't have given him that much time really."

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During the same campaign stop, Trump, continuing his feud with the Republican National Committee (RNC) and its chairman Reince Priebus, warned of a "rough July" if the GOP didn't sort out its "bad, bad system."

"They got to do something about, the Republican National Committee," Trump told the crowd. "They better get going, because I tell you what--you're going to have a rough July a that convention, you better get going, and you better straighten out your system, because the people want their vote."

Earlier in the day, before Trump hit the campaign trail in upstate New York, he expounded on his views of the Vatican meeting during an interview with Fox News.

"Five minutes sounds like, you know, 'try and get me in to see him so I don't get myself embarrassed before I come back to New York," the billionaire said. "A five minute visit, you can not do much."

"After you say hello," Trump added, "there's no time left."

Asked if he believed Sanders' visit with Pope Francis would "help with the Catholic vote" in New York, the GOP candidate said no, "i don't think so."

"It might help a little bit" for the state's April 19 primary, Trump predicted. But "it's a long trip and for a five-minute visit. You would think he'd stay in New York and campaign."

"If you're going to see the pope, you want to talk about a little bit of substance," he said.

Sanders took a day off campaigning in New York Friday to speak at a Vatican conference celebrating the 25th anniversary of an important Catholic encyclical. The short meeting with Pope Francis, which happened after Sanders' speech at the Pontifical Academy of Social Science, was an unscheduled gathering.

Both the pope and Sanders have said it lacked any political motive.

Sanders, the first Jewish candidate to win a Democratic primary, told CBS News' Seth Doane that he "chose not to do pictures" because "we didn't want anyone to think this was political."

And the pope told reporters that he greeted Sanders out of "politeness."

"This is called good manners, not meddling in politics," the Catholic leader said Saturday. "And if anyone thinks that to greet someone means to meddle in politics, then I suggest that they find a psychiatrist."

Trump's comments on the Vatican audience are not the first time the New York business mogul has butted heads with Pope Francis.

In February, after the pope implied that some of Trump's immigration policies were un-Christian, Trump called it "disgraceful" that a religious figurehead would question anyone's faith.

"The pope said something to the effect that maybe Donald Trump isn't Christian, okay? And he's questioning my faith, I was very surprised to see it," Trump said earlier this year. "For a religious leader to question a person's faith is disgraceful."