CAIRO — Orthodox Christian leaders meeting for a historic council aimed at promoting unity made a last-minute appeal Friday to the Russian Orthodox Church and three others to attend the gathering, the first such meeting in more than a millennium.

A spokesman for Istanbul-based Ecumenical Patriarch Bartholomew I said the leaders of 10 out of the 14 Orthodox churches that were supposed to convene on the Greek island of Crete will seek to resolve the issues that made the four churches decide not to attend.

“It will proceed, but they want their brothers with them and (now) make a plea even at the 11th hour” for them to attend, said the Rev. John Chryssavgis.

He said the church leaders met earlier on Friday and would later in the day send an official request for the other churches to attend.

“They will try hard to get their brothers to attend,” Chryssavgis said, adding that the leaders will reach out and ask the others: “How can we address your problems?”

The week-long Holy and Great Council is starting on Sunday. The four churches pulled out over the past two weeks after disagreements over procedural and some doctrinal issues. Except for Russia, they include Bulgaria, the Damascus-based Antioch Patriarchate and the Georgian Orthodox Church.

The meeting was meant to bring together the leaders of the 14 independent Orthodox churches to promote unity among the world’s 300 million Orthodox Christians.

Orthodox church leaders haven’t held such a meeting since the year 787, when the last of the seven councils recognized by both Orthodox and Catholics was held. The “great schism” then split the Roman Catholics and the Orthodox in 1054 amid disputes over the Vatican’s power.

The idea for the synod first emerged in the 1920s, but preparations began in 1961. Many preparatory meetings have been held since, the last one in Geneva in January 2016, involving representatives of all 14 Orthodox churches that were to attend the council.