Pope Francis will pray side by side with Orthodox patriarch Bartholomew in Jerusalem on May 25 during his visit to the Middle East in a powerful sign of Christian unity, the Vatican said on Thursday.

The prayer with the patriarch of Constantinople -- the spiritual leader of the world's Orthodox -- will take place in the Church of the Holy Sepulchre where Jesus Christ is believed to have died and been buried.

The two will also sign a "joint declaration", the Vatican said of the meeting, which is taking place on the 50th anniversary of a visit to Jerusalem by pope Paul VI and Constantinople patriarch Athenagoras.

The programme for the May 24-26 visit to Israel, Jordan and the Palestinian Territories released on Thursday also showed the pope will meet Palestinian and Syrian refugees and visit the Yad Vashem Holocaust memorial.