Theophilos Kuriakose, head of the Syriac Orthodox Church in Europe, called on Francis to raise the issue during a scheduled visit to Ankara on November 28.
"My humble request is that his holiness... Will take the opportunity to raise with the Turkish government the issue of the liberation of our brother bishops who have been kidnapped," he said.
The bishops, Boulos Yazigi and Yohanna Ibrahim, were kidnapped in Aleppo in northern Syria and unconfirmed reports have since suggested they are being held by Chechen militants on Turkish territory.