BOB ABERNETHY: A few miles from Camp David, Roman Catholic and Eastern Orthodox church leaders are meeting for a 10-day conference on their millennium-long split. There are about a billion Catholics around the world and roughly 300 million Eastern Orthodox. Dialogue between their leaders began officially 20 years ago, but it's been fraught with tension. Kim Lawton has our report on this summit, the first one ever in the Western Hemisphere.

KIM LAWTON: They have a common origin, tracing their roots to Jesus and his disciples. They share a belief in the Trinity, God as Father, Son, and Holy Spirit. And they have many similar sacraments. But their 1,000-year-old schism has been one of the bitterest divides in Christianity.

Father RON ROBERSON (National Conference of Catholic Bishops): You know, there was really very little sense of commonality, of communication between the two sides, and so you just had this kind of cold, icy silence that went on for a very, very long time -- for a period of centuries, in fact.

LAWTON: International delegates from both traditions are in Emmitsburg, Maryland, trying to negotiate more of a thaw. The closed-door meetings are reigniting an effort at international dialogue that began 20 years ago but has been stalled for the last seven years.

Archbishop STYLIANOS (Representative, Ecumenical Patriarchate): This dialogue between the Orthodox Church and the Roman Catholic Church is the most distinguished because it is the most difficult.

LAWTON: The most difficult because the tensions stretch back to the earliest days of Christianity. As the new faith became the official religion of the Holy Roman Empire, questions of doctrine and administration were addressed by councils of Church leaders from across the empire. But by the turn of the fifth century, the Roman Empire was politically divided into the Latin-speaking western empire, centered in Rome, and the Greek-speaking Byzantine empire of the East. Those political divisions put tremendous pressure on the Church.

Professor RANDALL MORRIS (William Jewell College): Between political divisions, language barriers, indeed, developing of traditions in isolation from one another, this just ended up magnifying the differences that at first were not significant, but in the end grew very large.

LAWTON: There were also crucial theological issues, such as the differing understandings of how the Holy Spirit fits into the Trinity and ecclesiastical authority.

In the East, the Church took on a more decentralized character, which continues today, with regional churches led by bishops of equal standing. The powerful bishop of Constantinople, the Ecumenical patriarch, was simply the first among equals.

In the West, there was a more centralized structure, headed by the bishop of Rome, the pope, who claimed Churchwide authority.

Fr. ROBERSON: The East has always been uneasy about the way the papacy has functioned within the Church, even back in the early centuries before the schism between East and West.

LAWTON: That formal split between the churches, known as the Great Schism, came in 1054. It was cemented with the Crusades, when western Crusaders attacked eastern Christians and sacked Constantinople during their efforts to recapture the Holy Land from the Muslims. A virtually complete chasm between the two churches continued until the 1960s, when the first overtures of peace began, overtures that led to a new openness for discussions.

Bridging 1,000 years of division isn't easy. This is only the eighth time this group has met since the dialogue was launched in 1979. The last meeting was seven years ago, when the talks ended in stalemate. This session was postponed three times, most recently last year because of tensions over NATO bombing in Serbia.