A split between the Russian Orthodox Patriarchate and a breakaway church-in-exile that dates back to the 1917 Bolshevik Revolution will be formally ended in May next year, church officials said Tuesday, according to Russian news reports.

Patriarch Alexy II of Russia and the New York-based leader of the Russian Orthodox Church Outside Russia, Metropolitan Laurus, will sign a document formalizing the reunification before conducting a joint service in Moscow on May 17, the officials said.

The Russian Orthodox Church's head of external relations, Metropolitan Kirill, said "there are questions that need to be settled, but these are formal details that will not influence the reunification act," ITAR-Tass reported.

In May this year, Clergy and lay delegates to a special council of the exile church in San Francisco voted to recommend that the bishops make the final decision to rejoin the mother church.

Each church still would maintain their own council of bishops, but priests could participate and lead Mass in both churches. The churches also could cooperate with religious education, youth programs and missionary activities.

The emigre church split from the Patriarchate three years after the Bolshevik Revolution and cut all ties in 1927, after Patriarch Sergiy declared the church's loyalty to the Soviet Union's communist government.

The Russian Orthodox Church had said that Sergiy's move was aimed at saving the church. It disavowed the declaration this year.

Talk of re-establishing ties began after the Soviet collapse in 1991. Both churches formed working groups after a 2003 visit to Russia by three emigre archbishops and a 2004 visit by Laurus.

Laurus emphasized that this is no "merger" and his branch will maintain administrative control over its 400-plus parishes worldwide. His group reports 480,000 U.S. members.