MOSCOW, Nov. 14 (RNS) -- While a first-ever papal visit next summer to Ukraine'slong persecuted Roman Catholic Church will boost local believers'morale, officials with the dominant Russian Orthodox Church say thepontiff's presence will worsen already strained relations between thetwo faiths.

The Russian Orthodox Church, the largest and most powerful of theEastern Orthodox churches, regards Ukraine as part of its religiousjurisdiction, despite the presence of an estimated 6 million Catholics.

"This is very significant. Ukraine is our canonical territory," saidIgor Vyzhanov, the Russian Orthodox Church's specialist in Catholicrelations. He added that a papal visit was undesirable as long as thetwo churches have yet to put aside long-standing disputes.

The leader of the 80 million-member Russian Orthodox Church, AlexiiII, routinely accuses Catholics of "proselytism" and "persecution" inUkraine.

Citing religious tensions, Alexii has steadfastly refused to meetwith Pope John Paul II, a Pole who has made better relations with theOrthodox one of his top ecumenical priorities.

After the 1989 legalization of Ukraine's Byzantine-rite CatholicChurch, Catholic clergy and believers emerged from the catacombs toreclaim property seized by Joseph Stalin in 1946 and turned over to thestate-sanctioned, Moscow-based Russian Orthodox Church.

Sometimes violent clashes between Orthodox and Catholicbelievers 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, protestsand general unpleasantness" if he visits the area.

A papal visit to Lviv, headquarters of Ukraine's Catholic Church, is almost certain, said Bishop Julian Gbur, secretaryof the church's synod, in a telephone interview.

"We have been waiting for the pope for about five years," said Gbur,an ethnic Ukrainian born just across the border in Poland. "My priestsand the bishops will be very happy."

Gbur said he expects a papal Mass in Lviv to draw up to 1.5 millionworshippers. The numbers will be especially large, he said, because aRoman pontiff has never visited Ukraine, which for centuries was part ofthe Russian Empire and, more recently, the Soviet Union.

"As you know it was an Orthodox country and there is no love for theHoly Father from them," said Gbur.

Officials at the Vatican Embassy to the Ukraine were more cautiousin their predictions for the papal visit -- said last week by theVatican to be tentatively set for June -- but were dismissive ofMoscow's idea of "canonical territory."

In a telephone interview from Kiev, a spokesperson at the Holy See'sembassy, who asked not to be identified by name, described the RussianOrthodox Church's notion of religious jurisdictions as "a medievalconcept. Who stops (them) from setting up eparchies or dioceses in theWest?"

Most religious observers in Moscow predict that the pope's visit toKiev -- the historical fountainhead of Russian Orthodoxy -- will ruinany chances for a meeting with Alexii II. But an Italian priest whoworked for decades with the underground Catholic Church in the SovietUnion, Father Romano Scalfi, predicted John Paul II's presence wouldhave a healing effect.

"Wherever the pope goes, it has helped cooperation, peace and betterunderstanding," said Scalfi, head of Christian Russia, a group hefounded in Milan in 1957. "If you look at the pope as a witness for theChristian church, he will help."

Scalfi, who visited Ukraine in September, said by telephone fromItaly that Orthodox-Catholic relations are better than in some of theother former republics because Ukraine's Byzantine-rite Catholics "havea very ecumenical spirit."

Historically, relations between Orthodox and Catholic hierarchieshave been acutely strained in Ukraine, which straddles the religiousfault line between Catholic West and Orthodox East.

In 1596, after lengthy negotiations with the papacy, the majority ofthe Orthodox hierarchy in Belarus and Ukraine agreed to join theCatholic 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 andagainst the union.

Thus was born what became the Byzantine-rite Catholic Church, alsoknown as the Greek Catholic, Uniate or Ukrainian Catholic Church.

Eventually the Russian czars forced most Ukrainian Catholics to returnto the Orthodox Church. To this day, it is difficult for most lay peopleto distinguish one from the other.

The pope's visit to Ukraine is made all the more complicated by athree-way split within the ranks of the country's Orthodox believers.The Moscow-based church remains the largest and most powerful but isbeing challenged by two others that split from Moscow after Ukrainebecame independent in 1991.