The Russian Orthodox Church, the largest and most powerful of the Eastern Orthodox churches, regards Ukraine as part of its religious jurisdiction, despite the presence of an estimated 6 million Catholics.
"This is very significant. Ukraine is our canonical territory," said Igor Vyzhanov, the Russian Orthodox Church's specialist in Catholic relations. He added that a papal visit was undesirable as long as the two churches have yet to put aside long-standing disputes.
The leader of the 80 million-member Russian Orthodox Church, Alexii II, routinely accuses Catholics of "proselytism" and "persecution" in Ukraine.
Citing religious tensions, Alexii has steadfastly refused to meet with Pope John Paul II, a Pole who has made better relations with the Orthodox one of his top ecumenical priorities.
After the 1989 legalization of Ukraine's Byzantine-rite Catholic Church, Catholic clergy and believers emerged from the catacombs to reclaim property seized by Joseph Stalin in 1946 and turned over to the state-sanctioned, Moscow-based Russian Orthodox Church.
Sometimes violent clashes between Orthodox and Catholic believers were a fixture of Ukrainian life in the early 1990s, especially in the area around the western Ukraine city of Lviv. Currently, relations are peaceful if not always cordial.
Still, Moscow's leading prelate in the region, Archbishop Avgustin (Markevych) of Lviv, has said the pope can expect "incidents, protests and general unpleasantness" if he visits the area.
"We have been waiting for the pope for about five years," said Gbur, an ethnic Ukrainian born just across the border in Poland. "My priests and the bishops will be very happy."
Gbur said he expects a papal Mass in Lviv to draw up to 1.5 million worshippers. The numbers will be especially large, he said, because a Roman pontiff has never visited Ukraine, which for centuries was part of the Russian Empire and, more recently, the Soviet Union.
"As you know it was an Orthodox country and there is no love for the Holy Father from them," said Gbur.
Officials at the Vatican Embassy to the Ukraine were more cautious in their predictions for the papal visit -- said last week by the Vatican to be tentatively set for June -- but were dismissive of Moscow's idea of "canonical territory."
In a telephone interview from Kiev, a spokesperson at the Holy See's embassy, who asked not to be identified by name, described the Russian Orthodox Church's notion of religious jurisdictions as "a medieval concept. Who stops (them) from setting up eparchies or dioceses in the West?"
Most religious observers in Moscow predict that the pope's visit to Kiev -- the historical fountainhead of Russian Orthodoxy -- will ruin any chances for a meeting with Alexii II. But an Italian priest who worked for decades with the underground Catholic Church in the Soviet Union, Father Romano Scalfi, predicted John Paul II's presence would have a healing effect.
"Wherever the pope goes, it has helped cooperation, peace and better understanding," said Scalfi, head of Christian Russia, a group he founded in Milan in 1957. "If you look at the pope as a witness for the Christian church, he will help."
Historically, relations between Orthodox and Catholic hierarchies have been acutely strained in Ukraine, which straddles the religious fault line between Catholic West and Orthodox East.
In 1596, after lengthy negotiations with the papacy, the majority of the Orthodox hierarchy in Belarus and Ukraine agreed to join the Catholic Church, provided they could keep the Eastern-rite liturgy, married clergy and administrative autonomy. Despite the bishops' agreement, violent clashes resulted between those believers for and against the union.
Thus was born what became the Byzantine-rite Catholic Church, also known as the Greek Catholic, Uniate or Ukrainian Catholic Church. Eventually the Russian czars forced most Ukrainian Catholics to return to the Orthodox Church. To this day, it is difficult for most lay people to distinguish one from the other.
The pope's visit to Ukraine is made all the more complicated by a three-way split within the ranks of the country's Orthodox believers. The Moscow-based church remains the largest and most powerful but is being challenged by two others that split from Moscow after Ukraine became independent in 1991.
A meeting between John Paul II and leaders of the breakaway Orthodox churches would give them a credibility they have lacked. No other Orthodox churches in the world have recognized either the Ukrainian Orthodox Church-Kiev Patriarchate or the Ukrainian Autocephalous Orthodox Church.
The larger of the two is the Ukrainian Orthodox Church-Kiev Patriarchate, headed by Patriarch Filaret. Patriarch Filaret -- a onetime leader in the Russian Orthodox Church by which he has since been defrocked, excommunicated and anathematized -- said in a recent interview in his Kiev office that he would gladly meet with the pope.
Patriarch Filaret said he sees a papal visit as a natural part of Ukraine's integration into Europe but cautioned, "We just don't want his visit to turn into a way to conduct proselytism."
The pope's itinerary is still in flux, but the Vatican Embassy spokesman in Kiev said he "is ready to meet with the Orthodox churches and with other churches."
This is the worst possible scenario for Moscow.
"If the pope goes there and meets with others, that is not acceptable. It is not desirable that he visit there in the first place but if he does go, he should only meet with Metropolitan Vladimir, the only canonical leader," said Catholic specialist Vyzhanov, in reference to the leading Russian Orthodox Church prelate in Ukraine.