The Vatican announced Friday that the pair will meet in Cuba next week, in the first gathering of its kind since the bitter 11th-century split that divided Christianity into Western and Eastern branches.
Each wing has since maintained that it is the true inheritor of the early Christian church established by the apostles of Jesus Christ.
"This historic meeting clearly marks a new stage in our relations," the Orthodox Church's spokesman Father Alexander Volkov told a press conference.
Volkov stressed that the meeting was not political in nature.
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"I can 100 percent guarantee that this is a meeting between two Church leaders that has nothing to do with politics," he said.
"The agenda of a church is not linked to the agenda of any country."
Patriarch Kirill, 69, is considered close to the Kremlin.
He has notably defended Russia's air campaign in Syria, which Moscow says is aimed at wiping out jihadists. The West accuses Russia of targeting more moderate factions that oppose President Bashar al-Assad, who Moscow supports.
A meeting between Francis and Kirill had been on the cards for some time with Francis saying in 2014 that he was willing to meet "wherever you want".