9 It is not surprising therefore that the bishops themselves, after vainly trying various remedies, concluded that the only hope for the Ruthenian Church lay in bringing about its return to Catholic unity. At that time the most powerful man among the Ruthenians was prince Constantine Ostrozhsky and he was in favor of this return, but only on condition that the whole Eastern Church should come to an agreement with the Western; later, when he saw that the plan was not going to be carried out in the way he desired, he became a violent opponent of the restoration of unity. None the less, on 2nd December 1594, the metropolitan and six bishops, after taking counsel together, published a joint declaration in which they proclaimed themselves ready to promote agreement and the long desired union. We have come to this determination, they wrote, "from the consideration, full of sadness for us, of how great are the hindrances men find in the way of salvation in the absence of this union of the Churches of God. From the time of Christ our Savior and his holy apostles, as the canons and councils make clear, our predecessors long continued in this union; they acknowledged one supreme pastor and first bishop in the Church of God on earth, no other than the holy pope of Rome, and obeyed him in all things. While this state of affairs remained in its vigor there was ever order in the Church of God and increase of divine worship."
Source: Orientales Omnes Ecclesias (Vatican.va)