But the clearest sign of all is expected to be the July 9-19 meeting in Emmitsburg, Md., of the Catholic-Orthodox international dialogue commission.
The meeting--closed to all, including the press, except for designated participants--will be the first for the commission since 1993 and the first to focus on theological questions since 1988.
While the 20th century closed with new tensions between Catholics and Orthodox, the new millennium seems to have dawned with new hope for Christian unity, said the Vatican's top ecumenist.
``I think that at the beginning of this new century, we have moved out of the really bad period of crisis and tension,'' said Cardinal Edward I. Cassidy, president of the Pontifical Council for Promoting Christian Unity.
The dialogue commission was formed in 1979 and in less than 10 years had produced statements of agreement on the Eucharist, sacraments, priesthood and apostolic succession.
Then political events in Eastern Europe led to the eruption of an issue which had been a bone of contention, but one kept in the background as areas of agreement were explored.
With the fall of communism, the persecuted Eastern Catholic churches were free for the first time in more than 40 years to function publicly.
That the Eastern Catholics' union with Rome meant a break with their mother Orthodox churches and that they continued to share a liturgical and spiritual tradition with the Orthodox long posed problems for the Orthodox.
But the long-standing difficulties became concrete obstacles to dialogue when Eastern Catholics, especially in Ukraine and Romania, began demanding the return of churches the countries' communist governments had given to the Orthodox decades earlier.
The Eastern Catholics also began gathering their members whom the communists in Ukraine and Romania had forced to become Orthodox or to express no religion at all.
The Orthodox, themselves recovering from communist oppression and persecution, charged Catholics with proselytizing in lands which traditionally had been Orthodox.
The Orthodox showed their displeasure by insisting that the two sessions of the dialogue which took place in the 1990s were devoted to discussing the practical issues raised by the re-emergence of the Eastern Catholic churches and by turning down Vatican invitations to several events, including sessions of the Synod of Bishops.
``There is no doubt we have moved away from that,'' Cassidy told Catholic News Service in late June.
While the formal dialogue was in suspended animation, Pope John Paul II made historic visits in 1999 to Romania and Georgia, his first papal trips to countries with an Orthodox majority.
And, when he went to the Holy Land in March, one of his warmest receptions came from Greek Orthodox Patriarch Diodoros of Jerusalem, who had pulled his church out of all bilateral dialogues in 1989 because, he said, other Christians were using them as a means of proselytism.
Cassidy said he thought the results of the pope's positive contacts with Orthodox leaders over the past year ``were pretty evident'' in the Orthodox participation at two Vatican jubilee events: the January opening of the Holy Door at St. Paul Outside the Walls and the May commemoration of 20th century martyrs at Rome's Colosseum.
While the meeting in Maryland should mark a return to dialogue on theological issues, it still will focus on the Eastern Catholic churches, each of which operates independently and stakes its own stand at the meeting, unlike the Vatican-organized Catholic side.
In 1993, Orthodox leaders and the Vatican declared together that although the Eastern Catholic churches were born of a desire for Christian unity, they did not achieve that goal and their method of union would not be an appropriate model to use in the future. At the same time, the Eastern Catholic churches' sincere faith and their right to exist cannot be questioned, they said.
Cassidy said the Orthodox churches agreed, but said the very existence of the Eastern Catholic churches raised theological and canonical questions which should be studied.
A key point is that for centuries the Eastern Catholic churches were seen as a sign that the Catholic Church believed their mother Orthodox churches did not have the means of salvation.
Cassidy said the 1993 document made clear the Vatican position that the Catholic and the Orthodox are ``sister churches,'' preserving apostolic succession and the sacraments and offering salvation to their faithful.
The cardinal said he hoped much will be clarified at the Emmitsburg meeting, but a return to the original schedule of themes for the dialogue would help even more.
``There is one important point on which we are still not agreed which is at the heart of all of this: being in communion with the bishop of Rome,'' the pope, he said.
``For us, that is an essential part of the faith, whereas for the Orthodox it is looked upon as not being essential,'' Cassidy said.
``Until we really have a consensus on that, we are struggling with the whole problem,'' he said.