The visit takes place as part of what has become a traditional exchange of delegations between the Orthodox Church and the Vatican for the respective feasts of their holy patrons.
The Holy See always sends a delegation to Istanbul on Nov. 30, feast of St. Andrew.
The Orthodox delegation will be made up by Metropolitan Emmanuel of France and director of the Orthodox Church's office in the European Union; Bishop Athenagoras of Sinope, auxiliary bishop of the Ecumenical Patriarchate serving in Belgium; and Archimandrite Maximos Pothos, the vicar-general in Switzerland.
On June 28, Benedict XVI will receive the delegation in audience, and on June 29, it will attend the Eucharistic celebration presided over by the Pope in St. Peter's.
The delegation will also meet with the Pontifical Council for Promoting Christian Unity.
The exchange of delegations between Rome and Constantinople began in 1969, with Cardinal Johannes Willebrands' visit to Constantinople for the feast of St. Andrew. At the time, the cardinal was president of the Secretariat for Christian Unity.