Pope Francis will host Vladimir Putin this week at the Vatican, playing international diplomat at a time when the Russian president finds himself excluded from the G7 summit and blasted by President Barack Obama and others over the conflict in Ukraine.

Francis has faced his own criticism over Ukraine, with Ukrainian church leaders reproaching the pontiff for not forcefully condemning Russia's takeover of Crimea. The pope has also called the fighting between government forces and pro-Russia separatists in Eastern Ukraine "horrible fratricidal violence," a remark that the head of Ukraine's Greek Catholic church said "reminded us of Soviet propaganda."

Experts say the pope is balancing the occasionally competing goals of bringing peace and calm to Ukraine, courting a stronger relationship with the Russian Orthodox Church, and avoiding the Ukrainian conflict becoming a religious war.

"The big picture is that the pope and Putin have had a pretty strong partnership on a variety of issues, so is that going to endure or will Ukraine upset the apple cart?" John Allen, an associate editor at the Boston Globe specializing in coverage of the Vatican and the Catholic Church, told VICE News.

According to Allen, the pontiff and the Russian leader have found common ground on Syria, with both leaders opposing the use of Western force to bring down the regime of President Bashar al-Assad. They have each also supported the easing of tensions between the US and Cuba, and called for the protection of Christians in the Middle East. Allen noted that Francis has been taking small steps toward mending the relationship between the Roman Catholic and Russian Orthodox churches, which have been at odds with each other for nearly a thousand years.

"The question," Allen said, "is whether Ukraine is going to derail all of that."

Francis has so far tread lightly in discussing the conflict in Ukraine, disappointing the country's orthodox church members, who view the pontiff as their leader and expect a stronger condemnation of Russian military aggression. The Greek Orthodox Church in Ukraine, which celebrates an orthodox liturgy but recognizes the pope as its leader, is one of the most active pro-democracy, anti-Moscow groups in Ukraine, Allen said.

"To date, they feel abandoned by Francis," Allen said. "They feel Francis is bending over backward to please Putin. There's enormous pressure for him to have their back."

But others said Francis has resisted condemning Putin in part because he is interested in building a relationship with the Russian Orthodox Church, which makes up some 70 percent of the 225 million Orthodox Christians worldwide.

'His major concern is that the war in Ukraine could become part of a religious narrative.'

"It's important for the pope and has been for the papacy for centuries to heal the breach between the Catholic and Orthodox world," Stephen Blank, a senior fellow at the American Foreign Policy Council who studies Russia, told VICE News. "The split between the East and the West is the original Christian rupture, so if you're serious about Christian unity, that's where you have to start."

Francis has made overtures to the leaders of Orthodox churches since his election, publicly praying with the head of Eastern Orthodox Church in 2014, and saying that he seeks communion with the Orthodox churches. And while his progress has not been significant thus far, he likely does not want to stop any potential progress in its tracks, Dennis Doyle, a theology professor at the University of Dayton, told VICE News.

"The pope's number one job is to try to maintain unity in the church, and when there's a schism, a split among churches, the number one job is to try to heal that split," Doyle said. "That is the office of the pope."

Photo by Alessandro di Meo/EPA

Doyle said that this particular visit between Putin and the pope is likely more political than ecumenical anyway, explaining that it gives the Russian president an opportunity to save face and meet with a high-profile leader during the G7.

"[Putin] is being isolated," Doyle said. "So he thinks of course that he's being excluded, he doesn't think it's his fault, he thinks what he's done has been rational, maybe not by Western standards but of course this is how Russia should be, that it should include more territory and have more access to waterways. So I think he's very wary of world opinion."

Pope Francis has also been reticent to speak forcefully on Ukraine because he is wary of the conflict tipping into an overtly religious divide, with the Russian Orthodox Church fighting against the Eastern Catholic Churches in Ukraine, some experts said.

"I think his major concern is that the war in Ukraine could become part of a religious narrative, where Catholics and Orthodox play a certain role that is given to them by their religious affiliation," Massimo Faggioli**, **a theology professor and Vatican expert at the University of St. Thomas in Minnesota, told VICE News.

Paul Stronski, a senior associate in the Russia and Eurasia program at the Carnegie Endowment for International Peace, agreed, telling VICE News that the pope "wants to preserve whatever progress has been made to the Catholic-Orthodoxy reconciliation."

"He's doing this to try and avoid it becoming a real religious war as opposed to the manufactured one it is," Stronski said.

Both the Vatican and Putin will release statements following their meeting, giving world leaders and the public some idea of what they discussed. Allen pointed out that they will likely spin the information differently, with the Vatican saying it was a constructive discussion about many world issues, including Ukraine, while Putin will likely boast of their agreement in defending Christians in the Middle East.

If there is significant progress in their discussions, or diplomatic success reminiscent of the pope's role in the Cuba-US relationship, the pontiff could let world leaders — including Obama — know in private communications or future discussions, Allen said.

But experts said major political maneuvering at this meeting is unlikely. Francis, rather than playing intermediary as he did with the US and Cuba, will likely be focused on his own interests, namely bringing about peace in Ukraine.

"What he wants to do is enhance the position of Vatican and improve conditions for Catholics everywhere," Blank said. "That's the standing goal of the papacy, but also this pope is an activist who believes he should help bring about solutions to disputes that otherwise seem unfruitful."

Doyle added that Francis "has a genuine drive to speak out on issues of justice and peace." He called the pope "an oddly provocative person, but in a peaceful kind of way."