Pope John Paul II (search) welcomed the spiritual leader of Orthodox Christians (search) on Tuesday, expressing hope the visit would help mend a historic rupture between the Eastern and Western branches of Christianity.

"We are praying that the Lord of history purifies our memories of every prejudice and resentment and allows us to freely proceed on the road of unity," John Paul said.

Ecumenical Patriarch Bartholomew I of Constantinople (search) met privately with John Paul hours before joining him for a late afternoon Mass in St. Peter's Square marking the feast day of St. Peter and St. Paul.

The pope has often appealed for rapprochement, but new strains have developed in recent years over what some Orthodox see as attempts by the Vatican to expand its reach in traditionally Orthodox parts of the former Soviet Union.

John Paul spoke of the visit in remarks at noon from his apartment window, as thousands of tourists and pilgrims gathered in the vast square below. The pope noted the meeting came 40 years after two of their predecessors — Pope Paul VI and Patriarch Athenagorus — met for a historic embrace in Jerusalem. Eastern Orthodoxy had long been isolated from the Western Church.

"That embrace has become a symbol of the hoped-for reconciliation between the Catholic Church and the Orthodox Churches, as well as a symbol of hope in the path toward full communion among all Christians," John Paul said.

The Churches split in the 11th century in disputes over the growing power of the papacy.

In his remarks welcoming the patriarch, John Paul recalled "important moments of contact" over the last 40 years — Bartholomew joined the pope at the Vatican in 1995 — as well as the "painful episodes of history" that have darkened their relations.

"In particular, we cannot forget what happened in the month of April 1204," the pope said, referring to the sacking of Constantinople by Crusaders that contributed to the collapse of the Byzantine Empire about three centuries later.

"How can't we not share, at a distance of eight centuries, the anger and the pain," the pope said.

The pope has expressed his remorse before, issuing a sweeping apology during a 2001 visit to Athens for the sins by Roman Catholics against Orthodox Christians, including the sacking of Constantinople.

The patriarch is called the "first among equals" of the five Eastern Church leaders.