VATICAN CITY -- As an unprecedented Vatican-U.S. church summit on clerical sex abuse got under way, U.S. participants said they were debating the central question of whether priests who abuse minors could ever receive another assignment.

Pope John Paul II told participants at the April 23-24 meeting's opening session that there was no place in the priesthood for "those who would harm the young," but also said church leaders could not overlook "the power of Christian conversion."

The closed-door meeting, held in a 16th-century room of the pope's Apostolic Palace, brought together eight ranking Vatican officials, three top officials of the U.S. bishops' conference and all but one of the 13 U.S. cardinals.

At a packed press briefing April 23 at the U.S. seminary in Rome, participants said issues raised at the first session included the potential reassignment of priests who have abused minors, strengthening the observance of celibacy, seminary screening and formation, and homosexuality.

In response to reporters' questions, they said calls for the resignation of Boston Cardinal Bernard F. Law, who is under fire for reassigning priest-abusers, were not mentioned.

But one of the prelates at the briefing, Cardinal Francis E. George of Chicago, said Cardinal Law raised the issue at a private meeting of the U.S. church leaders the night before the summit. He said the cardinal apologized to his colleagues, acknowledging that "if he had not made some mistakes, we would not be here."

The American cardinals were given the first part of the meeting to make individual presentations. Cardinal George said the mood was "serious, even somber."

After presentations from Vatican officials, the second day was to be devoted to an open discussion of proposals.

The Vatican said the pope would closely follow the meeting, but would not cancel previous engagements and audiences.

The 81-year-old pontiff told the participants he was "deeply grieved" by the clerical sex abuse, which he called a crime and an "appalling sin."

"There is no place in the priesthood and religious life for those who would harm the young," he said.

Cardinal George said church leaders at the summit were split on whether to adopt a "zero-tolerance" policy for priest-abusers, in large part because abuse of minors could encompass a broad variety of behaviors.

"There is a difference between a moral monster like (convicted pedophile former Boston priest John) Geoghan, who preys upon little children and does so in a serial fashion, and someone who perhaps under the influence of alcohol engages in an action with a 17- or 16-year old young woman, who returns his affection," he said.

The cardinal said civil law considers both to be crimes, but "in terms of the culpability and the possibility for a reform of one's life, they are two very different sets of circumstances.

"Given the civil law, can we make such a distinction in ecclesiastical policy? I'm not sure whether or not the present moment permits that distinction, so we might go toward zero tolerance," he said.

Another prelate at the briefing, Bishop Wilton D. Gregory of Belleville, Ill., president of the U.S. Conference of Catholic Bishops, suggested that an alternative to a flat "zero tolerance" policy might be to allow largely lay diocesan review boards to assist the bishop in deciding whether to reinstate an accused priest.

This would allow consideration of "mitigating circumstances" while still providing a "prudent and transparent solution" that assures parents their children are not at risk of harm, he said.

Cardinal George also supported lay involvement in implementing abuse policies.

"It seems to me to be clear that the more that lay people and others --including the relatives of victims -- are involved in applying the policies, the more credibility the actions of the bishop himself might have," he said.

But Cardinal Roger M. Mahony of Los Angeles said he read the pope's speech as support for a zero-tolerance policy.

"You can convert hearts and offer reconciliation, but you cannot reassign (priest-abusers)," the cardinal told one of his local television stations.

The pope, he said "is being as clear as he can be: There is no place for abusers in the priesthood."

Philadelphia Cardinal Anthony J. Bevilacqua said he thought the pope's remarks "could be read" as support for a zero-tolerance policy, but that the text required more study.

Cardinal Bevilacqua told Catholic News Service: "The Holy Father emphasized the horror of this scandal. He used the strongest words that I've ever heard him use in attacking this as a 'sin' and as a 'crime.' Using those words, he is showing that the highest priority and the first priority is being given to the children."

Another issue raised at the meeting was the potential link between the current crisis and homosexuality in the priesthood. Some church leaders have argued that most of the recently reported cases relate to homosexual activity, not pedophilia in the strict sense, since many of the victims were teen-age males.

In response to a reporter's question, Bishop Gregory said "a homosexual atmosphere or dynamic" in a seminary causes difficulties within the seminary and in recruiting candidates to the priesthood, because it can dissuade heterosexual men from pursuing a vocation.

But he suggested a serious effort to address the issue began after Vatican onsite studies of U.S. seminaries in the mid- and late-1980s.

"It is an ongoing struggle," he said. "It is most importantly a struggle to ensure that the Catholic priesthood is not dominated by homosexual men; (that) not only is it not dominated by homosexual men, but the candidates that we receive are healthy in every possible way: psychologically, emotionally, spiritually, intellectually."

Cardinal George said the question should not be whether a priesthood candidate is homosexual or not, but whether he is "capable of marriage and family, because an ordained priest is a married man" with the church as his bride.