Pope Francis (L) kisses Ecumenical Patriarch Bartholomew I after they signed a joint statement at St George church, the principal Greek Orthodox cathedral, on November 30, 2014 in Istanbul, Turkey

ISTANBUL (AFP) – Pope Francis on Sunday issued a strong pledge of support for the embattled Christians of the Middle East and urged an end to the millenium-old schism between the Orthodox and Catholic Churches, as he wrapped up his first visit to Turkey.

The trip of the pope to Istanbul — once the capital of the Christian Byzantine world and formerly known as Constantinople — has been marked by attempts to reach out both to Muslims and other Christian confessions.

The pope Sunday attended a divine liturgy led by Orthodox Ecumenical Patriarch Bartholomew I, the latest sign of the warming ties between the Roman Catholic and Orthodox Churches under his papacy.

Bartholomew, the “first among equals” of an estimated 300 million Orthodox believers, made a joint pledge with the leader of the world’s Roman Catholics to support Christians in the Middle East, saying they could not let Christianity be driven out of the region.

“We cannot resign ourselves to a Middle East without Christians, who have professed the name of Jesus there for two thousand years,” the Church leaders said.

Referring to the rampage of violence by Islamic State (IS) jihadists in Iraq and Syria, they warned that Christians in the region were being persecuted and forced from their homes.

They said the “terrible situation” of Christians calls “for an appropriate response on the part of the international community.”

Bartholomew 1 of Constantinople

The two church leaders also called on the parties involved in the Ukraine conflict “to pursue the path of dialogue and of respect for international law”.

– ‘Lengthy and rugged road’ –

Pope Francis in an address at the Patriarchate also urged an end to the Orthodox and Catholic schism to bring them back into full communion, saying the conflicts in the world had made unity even more urgent.

Bartholomew 1 kisses the head of Pope Francis

“The one thing that the Catholic Church desires, and that I seek as Bishop of Rome… is communion with the Orthodox Churches.”

“How can we credibly proclaim the message of peace which comes from Christ, if there continues to be rivalry and disagreement between us?” he said.

Batholomew for his part said that while the road to full communion would be “perhaps lengthy and sometimes even rugged” it was irreversible.

He echoed the pope’s comments that the violence against Christians had made this more pressing. “We no longer have the luxury of isolated action.”

The pope and Bartholomew have in the last months worked hard for a rapprochement between the eastern and western churches which have been split since the schism of 1054.

The reconciliation began in 1964 with the famous embrace in Jerusalem between Pope Paul VI and Ecumenical Patriarch Athenagoras, the first such meeting since the 15th century.

Bartholomew, who commands considerable respect beyond the Orthodox Church, holds an office that dates back to the early days of the Byzantine Empire, over a millennium before the Ottoman conquest of Constantinople in 1453.