The Pope's visit is unpopular with the Orthodox church

The enthusiasm in this city of baroque facades, cobbled streets and coffee-house charm is immense - but it barely conceals the underlying tension.

The Pope has rarely made a more contentious visit, and he is coming in the teeth of fierce opposition from the Orthodox Church.

The majority of Ukrainian believers are Orthodox, and most come under Moscow's jurisdiction. Patriarch Alexy II can barely conceal his fury. The Vatican has ignored his opposition to the visit.

He says that the time is not right - and relations between Ukraine's Greek Catholic Church and the Ukrainian Orthodox Church are too strained. The way he sees it, the Pope's visit will only make things worse.

Historial divide

The Russian Patriarch accuses the Greek Catholic Church in Western Ukraine of beating Orthodox priests, harassing believers and demolishing churches. What makes matters particularly painful for the Orthodox Church is that it sees the Greek Catholics as renegades.

For five decades Greek Catholics were banned from worshipping - either in public or privately

They broke away from Orthodoxy 400 years ago, but while they recognise the authority of Rome they still adhere to the Orthodox rite.

Today's bitterness, though, has its origins in more recent times. At a synod convened by Stalin at gunpoint in 1946, the priests of the Greek Catholic Church were given the option of exile and imprisonment or conversion to Russian Orthodoxy.

Thousands disappeared and for five decades Greek Catholics were banned from worshipping - either in public or privately. The Moscow patriarchate took possession of all their churches, and the six million Greek Catholics of western Ukraine have never forgiven it.

Father Demyan Bogun was one of those who suffered for his faith. Not much above five feet tall, he is now 92 and bent with age. I found him looking out onto the gardens of the medieval monastery of St Onufrii - a picture of tranquility in the rain-soaked warmth of early summer.

The Pope's trips abroad have caused controversy

His arthritic fingers twisted on his lap as he told me of his arrest over 50 years ago. Two guards stamped on his hands until his bones were shattered. Then they beat his kidneys and the soles of his feet until he lost consciousness.

He was sentenced to eight years imprisonment - seven of them spent in a labour camp in Siberia.

Like most Greek Catholics, he has no sympathy for Orthodox opposition to the Pope's visit.

Violent revenge

But Patriarch Alexy sees things differently. When Ukraine declared its independence 10 years ago, the Catholics took their revenge - sometimes violently. They seized back the churches they lost in 1946.

Alexy says the wounds inflicted then are still bleeding. And the persecution, he says, still goes on. He cited the case of the Church of St Vladimir in Lviv - which he claims the Greek Catholics have tried to destroy.

I went there to look for myself. He church lies in a bleak housing estate on the outskirts of Lviv. It is a wood cabin and dismissed contemptuously by local Catholics as "the barn".

Inside it is cold and damp, and water drips through the hard-board ceiling. Its poverty is in stark contrast to the Greek Catholic Church of the Nativity easily visible at the other end of the estate.

To your face, they're always fine and friendly, but they're Jesuits at heart. They say they want to help you but behind your back things are different

Father Vladimir Kuz'o, Orthodox priest

Five years under construction, the latter's massive walls and five gold cupolas gaze down contemptuously on poor St Vladimir's. There is no doubt which Church is in official favour - but no sign either that the Orthodox congregation is about to lose its building.

Father Vladimir Kuz'o is St Vladimir's priest. A kindly, decent man, he is deeply suspicious of the Pope. Like Alexy II, he accuses the Vatican of seeking to win converts from Orthodoxy.

"To your face, they're always fine and friendly," he says, "but they're Jesuits at heart. They say they want to help you but behind your back things are different."

As a native of neighbouring Poland, whose father served as an officer in Lviv when it was a part of the Austro-Hungarian empire, John-Paul II knows the dangers that lie ahead.

He wants to heal the rift between Catholicism and Orthodoxy, but his visit may prise them further apart.