MOSCOW, May 16 (RIA Novosti) - The leader of the Russian Orthodox Church opened Wednesday a "historical" session of the church's governing council, on the eve of the signing of a church reunification act after almost 90 years of separation.

On Thursday, Patriarch Alexy II and Metropolitan Laurus, the head of the Russian Orthodox Church Outside of Russia (ROCOR), will sign a document on reestablishing canonical ties, which is widely seen as a milestone on the way toward overcoming a decades-long rift with the foreign-based branch.

"This is a historical session of the Holy Synod... dedicated to a very important historical event - the signing of the Act on Canonical Reunification with the Russian foreign-based church," Alexy II told attending bishops.

"I think we are on the eve of a historical event when the tragic consequences of the civil war that divided our nation and divided our Church are to be eliminated," the patriarch said.

ROCOR was established by emigres who fled Russia following the 1917 Bolshevik revolution. The branch broke away in 1921, after accusing fellow clergymen in Soviet Russia of collaboration with the country's Communist regime.

Alexy II said President Vladimir Putin's meeting with Metropolitan Laurus in New York in 2003 greatly contributed to the reunification efforts, showing to ROCOR that "not a fighter against God, but an Orthodox Christian is at the country's helm."

The signing ceremony, timed to coincide with Ascension Day, will take place in Moscow's central Christ the Savior Cathedral.

A delegation of several dozen senior clergymen is accompanying Laurus on his historic Moscow visit. Hundreds of pilgrims from the United States and Western Europe have converged on the Russian capital to witness the event.