Pope Francis will hold a historic first meeting with Patriarch Kirill, the head of Russian Orthodox Church, in Cuba next week.
The Russian Orthodox Church said the “persecution of Christians” would be the central theme of the meeting.
Pope Francis will stop over in Cuba on his way to Mexico.
It is the first meeting of its kind since a schism between the Western and Eastern branches of Christianity emerged in the 11th Century.
The meeting is due to take place at Havana airport, where the two leaders will sign a joint declaration.
Patriarch Kirill is due in Cuba for an official visit at the same time as Pope Francis’ stopover in Havana.
In a joint statement, the two churches said the meeting would “mark an important stage in relations between the two churches”.
They invited ” all Christians to pray fervently for God to bless this meeting, that it may bear good fruits.”
Since becoming Pope in 2013, Pope Francis has called for better relations between the different branches of Christianity.