JERUSALEM — A rock on which the Virgin Mary is believed to have rested while on her way to give birth to Jesus has been uncovered by archaeologists just off the Jerusalem-Bethlehem road.

Identified by archaeologists as one of the major Christian sites ever excavated in the country, the site is expected to become a prime attraction for Christian pilgrims. It is certain to figure prominently in the year 2000 festivities, when masses of Christian visitors are anticipated from around the world.

The rock was the centerpiece of an enormous octagonal Byzantine church constructed in the fifth century. The church and adjacent monastery were destroyed in unknown circumstances in the eighth century, after the Arab conquest. Their remains were subsequently covered over and the precise location forgotten.

Scholars knew, however, from ancient documents of the church's existence and of the holy rock known as kathisma — the seat, in Greek.

The rock is not mentioned in the Christian Bible, but it is known from Christian documents dating from as early as the fourth century. Mary and her husband, Joseph, were traveling from Nazareth to Bethlehem, Joseph's birthplace, to participate in a census.

Tradition holds that the pregnant Mary rested on the large flat rock just off the ancient Jerusalem-Bethlehem road.

Plans to widen the present road led archaeologists to carry out an emergency dig and discover the stone and the surrounding church remains, including mosaic floors. The road-widening plans were duly altered.

At a press conference at the site Sunday, Antiquities Authority archeologists Rina Avner and Yuval Baruch, who uncovered the site, noted that the rock was slightly higher than the floor of the church around it and that it was exactly at the center of the structure. It was one of the earliest and largest churches dedicated to Mary.

Greek Orthodox Patriarch of Jerusalem Diodoros I, who visited the site Sunday, congratulated the authority on the discovery and said that his church would offer the authority full cooperation in making it accessible to visitors. "This great discovery has historical, religious and ethnic significance," he said.

The rock lies at the edge of an olive grove, on land owned by the Greek Patriarchate. The site was initially discovered in 1992, when a small emergency dig was carried out in connection with the road-widening plans. Its full dimensions were not exposed, however, until a contractor at the nearby Har Homa development site illegally laid a water pipe through the area a few months ago.