By Konstantin Eggert
The Russian Orthodox Church will be closely watching the selection of a new Pope in the Vatican after years of mutual distrust.
A man seen as the number two in the Moscow Patriarchate - Metropolitan Kirill of Smolensk and Kaliningrad - attended the funeral of Pope John Paul II.
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He handles external relations for the patriarchate and knows many cardinals.
There is speculation that he might have used the occasion to speak informally to Vatican officials about relations between the two churches, which have been troubled over the past 15 years.
The Orthodox Church accuses the Vatican of seeking to convert Russians to Catholicism.
Moscow Patriarchate also maintains that Orthodox worshippers in Western Ukraine suffer discrimination at the hands of the Ukrainian Eastern-rite Catholics, known as the Uniates.
The Uniates, with deep-rooted traditions in the region, have Orthodox rites but regard the Pope as their leader.
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Catholics reject the patriarchate's accusations, saying their missionaries work only among people undecided in their faith.
"The people who come to us are exercising their right to freely choose a faith - a right guaranteed by the Russian constitution," Metropolitan Tadeusz Kondrusiewicz, head of the Russian Catholics, told the BBC.
A representative of the Moscow patriarchate, Father Igor Vyzhanov, accepted that "this is all above board legally".
"But the Catholic Church calls the Orthodox Church 'a sister church' - and at the same time it is luring people whose cultural traditions belong to the Orthodox Church."
The Moscow Patriarchate speaks of a "canonical territory", meaning that only it has the right to carry out missionary work among Russians.
It was furious when in February 2002 the Vatican established a Catholic diocesan structure in Russia.
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The situation in Ukraine is potentially even more divisive.
The Uniates' leader, Cardinal Liubomyr Huzar, plans to move from Lviv to Kiev and hopes to receive the title of patriarch from the Vatican - an idea that alarms Moscow.
The Moscow Patriarchate totally rejects the notion that a non-Orthodox patriarchate could operate in Kiev, where Russian Christianity was born in 988.
Kiev is the residence of Metropolitan Vladimir, head of the Ukraine branch of the Moscow Patriarchate.
A senior Vatican envoy, Cardinal Walter Casper, visited Moscow last year and was told in no uncertain terms by Russian Patriarch Alexy II that such a move to Kiev by Cardinal Huzar would be "an unfriendly act". It could make the Moscow Patriarchate break off all ties with Rome, he hinted.
It remains to be seen whether Pope John Paul II's successor will risk backing Cardinal Huzar.
The Moscow Patriarchate always had a cautious approach towards John Paul II.
It suspected him, as a patriotic Pole, of anti-Russian feelings and of seeking to subordinate Moscow to Rome's will.
As a dedicated anti-Communist he was also a living reproach to the Russian Orthodox clerics who made compromises with the former Communist authorities.
Many observers expect an easing of Moscow-Rome tensions under a new Pope, who is unlikely to match Karol Wojtyla's energy and charisma.
At least two of his potential successors - Walter Casper and the Archbishop of Vienna, Cardinal Christoph Schoenborn, know the Orthodox faith well and want to activate dialogue with Moscow.
Many expect Alexy II to be better disposed towards the next pope - there is even speculation that he might finally allow a papal visit to Russia.
But some ultra-conservative clerics in the patriarchate dislike his efforts to reach out to other faiths. Despite being in a minority, they are influential.