The Pope's five-day visit to Ukraine - his 94th foreign visit - has prompted outraged protest from the largest Orthodox Church, which is linked to Russia's Orthodox Church. It has demanded the pontiff cancel the trip which begins on Saturday.
Bishop Mitrofan of the Ukrainian Orthodox Church Moscow Patriarchate, which boasts around 7.5 million worshippers, said his Church wanted the 81-year-old pontiff to stay away from its spiritual centre, the Pecherska Lavra monastery in Kiev.
"We will stage all-night prayers near the Lavra and St. Sophia's Cathedral to prevent the Pope visiting our sacred places," Mitrofan told a news conference in the monastery.
Although the Pope is not expected to visit Pecherska Lavra, a magnificent complex of gold-domed churches which is the Ukrainian capital's main tourist attraction, Mitrofan's comments reflected his Church's anger at the visit.
Both Russia's Orthodox Church and its Ukrainian affiliate accuse the Pope of seeking converts in Ukraine and say the visit will worsen relations between the Orthodox and Catholic branches of Christianity.
The Moscow Patriarchate sent the Vatican a letter in January asking the Pope to postpone indefinitely his trip - a move dubbed "not Christian" by Ukraine's main Catholic Church.
The Pope said in Rome earlier this week that he was going to Ukraine with "great hope" for his pastoral visit to Ukraine's six million Catholics, many of whom live near the western city of Lviv which will be the second leg of the Pope's trip.
"My objective is to confirm the faith of our brothers and sisters of the Catholic community, and also to promote ecumenical commitment in the words of Christ: 'May they all be one!"' he said.
But Mitrofan said the visit could only harm Ukraine, a country of 49 million bordering the Black Sea, Russia and eastern Europe.
"This visit will only split our society," he said. "It won't bring us peace as promised, but only problems."
Mitrofan's statement came a day after the leader of a rival Church, Patriarch Filaret of the Ukrainian Orthodox Church Kiev Patriarchate, told Reuters he welcomed the visit as a chance to work towards healing the division of Christianity, which split into western and eastern branches in 1054.
"The Pope is a wise and authoritative person and his objective is to help the reconciliation of the churches," he said in an interview. "This fact allows us to hope that the Pope's visit will, in fact, help improve relations."
But Mitrofan, whose Church excommunicated Filaret as a "schismatic" after the collapse of the Soviet Union, said the Pope's visit would also deepen the rift between Ukraine's fragmented Orthodox Churches.
"After the visit the slit between the churches will be even bigger," he said. "The visit won't bring the Ukrainian people any good."
On Thursday, carrying icons and signs saying "Orthodoxy or Death," some three-thousand followers of the Moscow-based Russian Orthodox Church marched through Kiev protesting the Pope's visit.
Ukraine will be the fifth former Soviet country the pope has visited, but the trip will be more delicate than visits to Lithuania, Latvia and Estonia in 1993 and Georgia in 1999.
While religious tensions in those countries have eased in the past dozen years, they are rife in Ukraine, where Western and Eastern Christianity mix, clash, and sometimes explode.
In 1946, Soviet dictator Josef Stalin suppressed the Eastern Rite Catholic Church, known as the Greek Catholic Church, and gave its property, including churches, to the local
Orthodox Church, which was run from Moscow and was pro-government.
The Eastern Rite Catholics worship in a Byzantine rite used in the east since the Great Schism of 1054. But they owe their allegiance to the Vatican.
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