The visit, which was confirmed June 4 by the Holy See’s chief spokesman, Fr. Federico Lombardi, will be Putin’s second meeting with Francis. The two leaders also met in the Vatican in November 2013.

But the ground between Moscow and Rome has shifted significantly in the interim, with Russia annexing the Crimea Peninsula last year and being accused of fomenting the ongoing war in eastern Ukraine.

The Pope has previously expressed concern over the conflict; in his Easter message he wished for Ukraine to “rediscover peace and hope thanks to the commitment of all interested parties.”

But Francis’ decision not to specifically mention Russia has led to disappointment among Ukrainian Catholics — and speculation over whether the Pope will raise the issue with Putin in their private meeting.

The two leaders may also revisit their earlier discussion of the Syrian war, a crisis the Pope has highlighted repeatedly and one in which the Kremlin plays an important role.

Faith in the Pope’s diplomatic skills are not unfounded: He turned out to be a key player in brokering a historic deal between the United States and Cuba last year.

Francis is also not one to shy away from controversy: He stirred a political storm with Turkey in April when he used the term “genocide” to refer to the mass murder of Armenians a century ago.

No pope has ever visited Russia, in part because of Kremlin concerns over the pontiff’s public appeal, and also because of long-standing tensions between Roman Catholicism and the Russian Orthodox Church, which under Putin has returned to its role as a champion of nationalist pride.

It was notable that Putin did not invite Francis to visit when the two first met, one of the few national leaders not to publicly extend such an invitation to the popular Pope.