The Russian Orthodox Church has said it will not attend a historic meeting of all of the world's Orthodox churches calling for a postponement as other churches have pulled out.

Discussion on the Holy and Great Council, or the Pan-Orthodox Council, to have been held on the Greek island of Crete began first in 1961.

It was due to take place from June 16-25 as the first council of its kind since the eighth century.

"There are many problems among various Orthodox churches... These disagreements might seem small but, for historical churches, these are important issues," the head of external church relations and member of the Holy Synod of the Moscow Patriarchy, Metropolitan Hilarion, told Russia Today June 14

The council was supposed to bring together all 14 "autocephalous" Orthodox churches, the largest number ever to have come together.

But after the Bulgarian church pulled out for reasons which remain unclear, the Moscow Patriarchate said the meeting could not go ahead unless all the churches were present, the Catholic Herald reported.

Metropolitan Hilarion of Volokolamsk gave comments at a media briefing on the decisions of the Holy Synod of the church.

"All churches should participate in the Pan-Orthodox Council, and only in that case its decisions will be legitimate," he said.

The landmark meeting of the heads of all Orthodox Christian churches could be postponed as five out of 14 churches have pulled out, Russia Today reported.  

Pope Francis was to have sent a high-level observers to the Crete meeting as a gesture of support for the Orthodox Church, the Catholic Herald reported.

Ecumenical Patriarch Bartholomew of Constantinople invited Pope Francis to send observers to the meeting and the pontiff chose Cardinal Kurt Koch and Bishop Brian Farrell of the Pontifical Council for Promoting Christian Unity.

In the meantime 50 Orthodox scholars have signed an open letter to Orthodox leaders, urging them to come together for the Pan-Orthodox Council.

The scholars, many of them from U.S. universities and part of the Orthodox Church in America sent their open letter sent to the 14 Primates of the churches.

In it they wrote, "The Holy and Great Council occasions an opportunity to commence a new phase of Orthodox witness. As the eyes of the whole world are upon the Orthodox Church, we beseech all of our leaders to hear the Spirit's call to conciliar unity."

BULGARIAN ORTHODOX CHURCH

The Bulgarian Orthodox Church's leadership was widely seen as strongly influenced by their Russian co-religionists, with the Moscow church seen by critics as determined to spoil a council decades in preparation, the Sophia Globe reported.

But a Bulgarian metropolitan denied that his church's position was taken under external influence.

"The Bulgarian Orthodox Church takes its decisions completely independently and not under external pressure," Antonii, Bulgarian Orthodox Church Metropolitan of Western and Central Europe, told a television interviewer earlier in the week.

The Russian Orthodox Church is said to have 100 million followers making it largest church among some 300 million Orthodox believers, The Moscow Patriarch Kiriill is close to President Vladimir Putin.

Istanbul-based Ecumenical Patriarch Bartholomew is often described as as "the first among equals" among Orthodox Christians and is senn by many as the spiritual leader.

Bartholomew has met Pope Francis a number of times and Kirill met the Catholic leader at a historical Havana encounter in Feburary.