The Roman Catholic Church formally apologized today for failing to take more decisive action in challenging the Nazi regime during World War II to stop the extermination of more than 6 million Jews.

But in a long-awaited document on the church's role in the Holocaust, the Vatican defended Pope Pius XII, who headed the church during the war, from accusations that he turned a blind eye to the systematic killing of Jews. Some critics say Pius was motivated by church religious prejudices dating back to the death of Jesus Christ.

Pope John Paul II, in a preface to the landmark publication entitled "We Remember: A Reflection on the Shoah," expressed hope that the historic declaration of repentance by the Vatican about Catholic shortcomings in dealing with the Holocaust "will indeed help to heal the wounds of past misunderstandings and injustices."

First reactions from Jewish leaders in Israel and the United States were mixed, however, suggesting the Vatican's effort to achieve the pope's objective had fallen short of their expectations.

More than any of his predecessors, John Paul has made reconciliation with the Jewish people a major priority of his papacy. During his 20-year tenure as leader of the world's 1 billion Catholics, he has become the first pope to visit concentration camp sites and to preach in a synagogue. He pushed the Vatican to open diplomatic relations with Israel in 1993 and hopes to celebrate the millennium with leaders of Jewish and Islamic faiths in an extravaganza of monotheistic religions on Mount Sinai.

At a meeting in 1987 with Jewish leaders at his summer residence in Castel Gandolfo, Italy, the pope promised them that the Vatican would publish the church's history in dealing with antisemitism and the genocide of European Jews. It was the first time Jewish representatives had held informal discussions with the pope, who insists that Christians must overcome centuries of animosity and learn to regard Jews as their "older brothers."

"We deeply regret the errors and failure of those sons and daughters of the church," the Vatican paper said. "We cannot know how many Christians in countries occupied or ruled by the Nazi powers or their allies were horrified at the disappearance of their Jewish neighbors and yet were not strong enough to raise their voices in protest."

Jewish leaders in Israel and the United States generally expressed disappointment with the document, the most definitive Vatican statement to date on the church's role in the Holocaust.

Meir Lau, Israel's chief rabbi for Jews of European ancestry, said he was thankful that "after two thousand years of hostility between the church and Jewish people, there is something new, a new atmosphere happening before our eyes." But he bluntly rejected the document's conclusions about Pius XII.

"His silence cost us millions of lives," Lau said in Tel Aviv. "One who stands upon the blood and does nothing to avoid the bloodshed is like a partner to the mass murder of human beings. He didn't do it, but he didn't stop it."

"It falls quite short of what was hoped for," said Efraim Zuroff, director of the Simon Wiesenthal Center in Jerusalem. "Unfortunately, it does not unequivocally take responsibility for the teachings of the church that created the atmosphere that ultimately led to the Holocaust, and to the participation of numerous believing' persons in that crime."

Robert S. Rifkind, president of the American Jewish Committee, called the document a "step in the right direction for the future of Catholic-Jewish relations." However, he added, "it only begins to address many issues and questions concerning the role of the Catholic Church in the evolution of antisemitism throughout the ages and its culmination in the {Holocaust}. It tells the truth, but not the whole truth."

Phil Baum, executive director of the American Jewish Congress, criticized the Vatican's failure to "impose moral culpability on some leading church authorities . . . who were either indifferent or in some cases actually complicit in the persecution of Jews."

The document praised the "wisdom of Pius XII's diplomacy" and cited his warning in a 1939 encyclical "against theories which denied the unity of the human race and against the deification of the state," which he feared could culminate in a terrible "hour of darkness."

The paper contends that Jewish leaders supported the view that Pius helped save hundreds of thousands of lives. It cites the words of Golda Meir, the former Israeli prime minister, who eulogized Pius upon his death in 1958 for raising his voice "when fearful martyrdom came to our people."

Vatican historians say that Pius worked quietly behind the scenes and did not take a more assertive attitude in denouncing Nazi transgressions because he feared that such a brazen stand would have little helpful effect and would worsen conditions for Catholics, as well as Jews, in Germany and Nazi-occupied countries across Europe.

Cardinal Edward Cassidy, the head of the Vatican Commission for Religious Relations with Jews, defended the document as a historic confession of Christianity's failure to prevent the Holocaust. He said the paper went much further than addressing demands by some Jewish groups for an apology about the church's behavior during the war.

"This is an act of repentance," the Australian cardinal told reporters after the document was released. "This is more than an apology since as members of the church we are linked to the sins as well as to the merits of all her children."

Cassidy added: "We feel we have to repent. Not only for what we may have done individually, but also for those members of our church who failed in this regard."

The document clearly bears the imprint of John Paul, who grew up under the Nazi occupation of his native Poland. He has said that with the approach of Christianity's third millennium, Catholics must take pains to examine responsibilities for the evils of history, especially the Holocaust, which he describes as an "indelible stain" on the 20th century.

"The Church should become more fully conscious of the sinfulness of her children, recalling all those times in history when they departed from the spirit of Christ," the document reads. It cites John Paul as noting that while some Christians acted courageously during the Holocaust, "the spiritual resistance and concrete action of other Christians was not that which might have been expected."

The document acknowledges that Christians have been guilty of much anti-Jewish prejudice over the past two millenniums. The church itself did not repudiate the notion of collective Jewish guilt for Christ's death until the early 1960s, when the Second Vatican Council, under Pope Paul VI, released the most significant paper on Jewish relations until now.

But Vatican historians drew a sharp distinction in the current document between anti-Jewish resentments that have tarnished Christian history and the diabolical hatreds that drove the Nazi dictatorship of Adolf Hitler to carry out the genocide of European Jews.

"The Shoah was the work of a thoroughly modern neo-pagan regime. Its antisemitism had its roots outside of Christianity and, in pursuing its aims, did not hesitate to oppose the Church and persecute its members, also," the paper says. "The Catholic Church repudiates every persecution against a people or human group anywhere, at any time. She absolutely condemns all forms of genocide, as well as the racist ideologies that give rise to them." Correspondents Doug Struck in Jerusalem and John M. Goshko at the United Nations contributed to this report. CAPTION: Vatican officials, from left, the Rev. Remi Hoeckman, Bishop Pierre Duprey and Cardinal Edward Cassidy, discuss Holocaust document with journalists.