The leader of the Roman Catholic Church and the spiritual heirs of Martin Luther met here today in a candid hour-long session that reflected the continuing divisions as well as the desire for unity within the Christian world.

Pope John Paul II, in what may be the most important meeting of his five-day visit to West Germany, acknowledged to Protestant church leaders that the Catholic Church shared the blame for the five-century-old break within Christianity but he insisted that unity of worship must await doctrinal unity, a position that one Lutheran leader called "painful."

A Protestant spokesman nonetheless described the talks as "friendly and brotherly" and church officials announced afterward that a special commission will be formed to study ways on reconciling further the differences between Catholic and Protestant churches.

Improved cooperation between Christianity's two major branches has been a central theme of the pope's visit to West Germany, the birthplace of the 16th century Protestant Reformation. The country's population of 63 million is equally apportioned between Catholics and Protestants, most of whom are Lutherans, known in Germany as the Evangelical Church.

"We must keep up the dialogue and the contacts. We must leave no stone unturned," John Paul told the Lutheran leaders. "We owe it to God and to the world."

While the new commission could not be considered a major breakthrough -- and its exact membership and schedule of meetings have still to be worked out -- it does represent the most concrete development in the pope's visit, the first papal pilgrimage to Germany in nearly two centuries. Together with remarks deferential to the ecumenical movement made by John Paul since his arrival Saturday, its formation was seen by religious circles here as a boost for recently stagnated efforts at interfaith cooperation.

In a clear gesture promoting Christian unity, John Paul conceded today that the Roman Catholic Church was not blameless for the division of Christianity 450 years ago, when Luther and Rome split.

"We want to admit to each other guilt . . . Everyone has sinned in the past," John Paul told the seven-member Protestant delegation seated with him and a six-man Catholic delegation in a room of the museum in the Mainz cathedral.

From the start of his visit here, the pope has seemed intent on heartening West German Protestant leaders who had been disappointed that his visit to Martin Luther's native land had not been conceived as more of an ecumenical event. Today's meeting, in fact, was only a last-minute addition to the crowded papal itinerary.

Keenly aware of the historical resonance of the moment, John Paul began his address by recalling Luther's pilgrimage to Rome in 1510. "Today, I come to you, the spiritual heirs of Martin Luther, and I come as a pilgrim," the pope declared.

But despite the conciliatory tone of his opening remarks, John Paul remained inexorable toward Protestant urgings for joint communion.

This issue was sharply outlined in a statement that proceded the pope's by Bishop Eduard Lohse, chairman of the German Evangelical Church Council.

"We are painfully aware that we have not been able to win full agreement with our brothers and sisters of the Roman Catholic Church on the eucharist," or the reception of communion, Lohse told John Paul. "We wait with patient hope for an invitation from your church showing that we are welcome as guests and friends at the celebration of the eucharist without giving up our own church membership for it."

The Catholic church considers the communion bread the actual body of Christ, a doctrine rejected by Protestants, and it requires acceptance of this doctrine for participation in the communion service.

John Paul, responding to Lohse's plea, made clear that Christians of both faiths could assemble around one alter only after full unity of thier churches was achieved. "Only full unity will allow us to gather around the Lord's table in one spirit and belief," he said. He also warned that good will shown on both sides "should not make us blind to the divisions that still stand between us."

John Paul said the complexity of the problems to be solved required a more comprehensive discussion than today's one-hour meeting allowed. But he urged continuation of the ecumenical dialogue that started with a 1962 Vatican meeting that set the aim of unifying Christian churches.

Earlier, in a meeting with West German Jews, John Paul said the two faiths could work together for justice and peace in the world as well as better understanding between themselves.

"The strong, brotherly relations between Jews and Catholics in Germany gain a special value against the background of persecution and attempted extermination of Jews in this country," the pope said.

He will visit Altotting and Munich before returning to Rome.