The head of the Russian Orthodox Church, Alexiy II, told an Italian paper that a first meeting with Pope Benedict would only make sense if the Vatican gave up any missionary ambition to spread Catholicism in his country.

The Russian Patriarch, in comments to Il Giornale published on Wednesday, laid out clear conditions for a meeting between the leaders of the eastern and western branches of Christianity, which split in the Great Schism of 1054.

"The meeting between the Pope and the Patriarch of Moscow must be well prepared and must run absolutely no risk of being reduced to an opportunity to take a few photographs or appear together before television cameras," he said.

"It must be an encounter that really helps to consolidate relations between our two churches."

The break-up of the Soviet Union in 1991 brought increased tension between the Vatican and the Russian Orthodox Church, with clerics in Moscow worried about new opportunities for so-called "soul-poaching" by western Catholics.

Senior Catholic cardinals now say a first ever meeting between a Pope and a Russian Patriarch is increasingly likely. Popes have in the past met Ecumenical Patriarchs, the spiritual leaders of the worldwide Orthodox church based in Istanbul.

But centuries of rivalry cannot be forgotten easily.

"Still today some Catholic bishops and missionaries consider Russia as missionary terrain," the Patriarch said.

"But Russia, holy Russia, is already illuminated by a faith that is centuries old and that, thank God, has been preserved and handed on by the Orthodox Church," Alexiy told Il Giornale after greeting some Italian Catholic bishops in Moscow.

"This is the first point of the problems that need to be clarified and smoothed over regarding a meeting with the Pope."

Another concern, he said, was the spread of "eastern rite" Catholicism throughout former Soviet states. Eastern Catholics have the same Mass as Orthodox churches but, unlike them, have been in full union with the Vatican since the 17th century.

Alexiy said the eastern rite was now spreading to "areas where it never used to exist, such as eastern Ukraine, Belarus, Kazakhstan and Russia itself".

Banned in 1946 by dictator Josef Stalin and its property handed over to the more compliant Orthodox church, the eastern rite was permitted again the dying days of Soviet rule.

"When these problems are confronted and resolved then the meeting between the Pope and the Patriarch of Moscow will be possible. Then it will have real significance," said Alexiy.