Sen. Bernie Sanders will make an unusual campaign stop next week, when he flies to Italy to meet with Pope Francis at the Vatican.

Sanders was invited by the Vatican to visit on April 15, just four days before the New York primary, as apart of a conference on social, economic and environmental issues, and Sanders will discuss how to incorporate morality into the global economy. The conference will be hosted by the Pontifical Academy of Social Sciences, and it's meant to commemorate the 25th anniversary of an important encyclical by Pope John Paul II.

"I am delighted to have been invited by the Vatican to a meeting on restoring social justice and environmental sustainability to the world economy," Sanders said in a statement. "Pope Francis has made clear that we must overcome 'the globalization of indifference' in order to reduce economic inequalities, stop financial corruption and protect the natural environment. That is our challenge in the United States and in the world."

On "Morning Joe" Friday, Sanders said he and the pope don't agree on all issues, but he credited Francis for leading the charge on these kinds of problems.

"I am a big, big fan of the pope," Sanders said on "Morning Joe." "People say Bernie Sanders is radical. Read what the pope has wrote!"

The Vermont senator is a non-practicing Jew who never talks about religion on the campaign trail, but when asked about his religious philosophy during a previous Democratic town hall, he cited the "golden rule" as the code he lives by. Additionally, both Sanders and the pope emphasize the importance of climate change and social justice to their supporters.

The visit has a chance of boosting his vote total in the primaries, as there are many Catholic voters in the remaining primary states such as New York, New Jersey and Pennsylvania.

Along with Sanders, prominent attendees at the Vatican event include Ecuadorean President Rafael Correa, Bolivian President Evo Morales and academicians of the Pontifical Academy of Social Science.