The announcement said Francis has called for this "ecumenical encounter for peace" in view of the "dramatic situation" facing many Christians in the Middle East.
The pope has frequently decried violence targeting Christians in parts of the Middle East, many of whom have fled their homelands to seek safety.
St Nicholas Basilica in Bari, an Adriatic port city, is a popular pilgrimage destination for both Catholics and Orthodox Christians.
The Vatican said Francis is calling for prayers to help prepare for the day-long event.
Reporting by Associated Press.
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