VATICAN CITY (RNS) When Pope John Paul II travels to Greece this weekend to follow "in the footsteps of the Apostle St. Paul," he will be putting his formidable powers as a communicator and ecumenist to a tough new test.

Rarely in the 22 years of his peripatetic pontificate has the now frail but still determined Karol Wojtyla been less welcome as a guest. And rarely has the deep rift between Roman Catholicism and Eastern Orthodoxy been so painfully apparent.

Barring changes of plan, the Greek Orthodox Church will send no representative to the Athens airport to welcome the 80-year-old pontiff when he becomes the first pope in history to set foot on Greek soil Friday (May 4).

When John Paul meets Archbishop Christodoulos of Athens and all Greece later in the day, the head of the Greek Orthodox Church is expected to read a list of grievances and invite the pope to ask forgiveness for his church's past offenses.

When the pope goes to the Aeropagus hill near the Acropolis where St. Paul is said to have first preached to the Gentiles, Christodoulos will be present and there may be a common Catholic-Orthodox statement but there can be no common prayer, Greek Orthodox spokesmen say.

And when the pope celebrates Catholic Mass in Athens the next morning (May 5), he will do so, barring last-minute changes, in a small, covered stadium that seats only 17,000 while Greece's Roman Catholics alone number far, far more.

"The pope has no invitation from the Church of Greece," said Simeon Svanas of the press office of the archbishopric. "He was invited by the government. And there can be no common prayer."

John Paul has made improving relations with the Eastern Orthodox-which split with Rome in 1054 over a number of theological issues-a key part of his pontificate.

But despite statements from both sides that they would like to heal the schism, obstacles -- including the role of the papacy and Orthodox suspicion of Catholic proselytism in predominantly Orthodox countries-have remained intractable.

John Paul first expressed his desire to visit Greece in 1999 as part of his planned Jubilee Year pilgrimages to sites of the Old and New Testaments. But the Greek Orthodox Church vetoed any such trip until Greek President Costis Stephanopoulos forced the issue this year by formally inviting the pontiff during a visit to the Vatican on Jan. 24.

The Holy Synod, or governing body, of the Greek Orthodox Church then lifted its veto, causing violent reactions from some Orthodox circles, including virtually all of Greece's monastic communities, a numerically small but politically powerful voice in the Greek church.

The monks of Mount Athos issued a statement charging that the true goal of the pope's trip is "to demonstrate to the world that he is the spiritual leader of Christianity." Last week they gathered with other monks at Mount Olympus for 24 hours of prayer that the pope's visit will be canceled.

Hostile posters have gone up in Athens describing the pope as "arch-heretic" and "two-horned, grotesque monster of Rome." And a series of protest demonstrations have been organized.

Reacting to the events in Greece, some Catholic clergymen in Rome now openly accuse the Greek Orthodox of provincialism and downright rudeness.

"People in the modern world with a modicum of education and decency do not use offensive language when dealing with others, even if they may be of different beliefs," said the Rev. Robert Taft, an American who is vice rector of Rome's Pontifical Oriental Institute.

"The pope is an old, old man who is trying his level best to do what he can to heal the wounds of the past," Taft said. "His hands are outstretched, his heart is open, he's not going there to rattle anybody else's cage. Anybody who does not take that hand is making a statement not about the pope but about himself."

Belgian Father Michel Van Parys, who works at the Vatican's Congregation for Oriental Churches, says he thinks "there is a widespread impression in Greece that the Latin Church is just trying to subdue the Orthodox Church."

"On the Catholic side, it is just a pilgrimage in the steps of St. Paul. There is nothing more," Van Parys said. "But that's not the way the Orthodox people see it."

Van Parys said he thinks the Greek Orthodox people question the sincerity of the Roman Catholic Church, which has absorbed a number of Eastern rite churches in recent centuries. He believes they cannot forget the sack of Constantinople of 1204 when Crusaders killed thousands of Orthodox Christians, desecrated churches and icons, installed Latin bishops and carried priceless spoils back to the West.

"I think that for the sensitivity of the Greek Orthodox people, 1204 is a symbolic date that shows the aggressiveness of the Latin West and Latin Church," Van Parys said.

"Our faith," said anti-pope radical Theodoros Zisis of the University of Thessaloniki's School of Theology, "teaches us that the pope and papism are not church.

"The sacred scriptures forbid communication with heretics," Zisis said. "The popes transformed a church of humility and love into a church of wars and aggression."

Ioannis Karavidopoulos, also of Thessaloniki University's School of Theology but more of a moderate, said he hopes the pope will have the "self-knowledge and the decency" to ask pardon for the injustices of the past.

"If he asked pardon it would be very significant," Karavidopoulos said. "But it would have to be with sincerity, not just for political correctness."