VATICAN CITY - American clergy sex abuse victims brought their campaign for reform today to the center of Roman Catholicism, demanding Vatican officials bar Cardinal Bernard Law from celebrating an important Mass mourning Pope John Paul II.

Two leaders of the Survivors Network of those Abused by Priests, who arrived in Rome just hours before the service Monday at St. Peter's Basilica, condemned what they called the Vatican's "hurtful decision" to choose Law for the honor.

Law resigned as archbishop of Boston in December 2002, after unsealed court records revealed he had moved predatory clergy among parishes without alerting parents that their children were at risk. More than 550 people have filed abuse claims in Boston in recent years and the archdiocese has paid more than $85 million in settlements.

American cardinals generally have declined to comment on Law's celebrating one of the nine daily Masses for John Paul, a period of mourning called Novemdiales. But some have said the Vatican likely chose him become he leads an important church, not to give him a personal honor. St. Mary Major is one of four basilicas under direct Vatican jurisdiction.

Still, the assignment gives Law a position of influence. In their homilies, cardinals can highlight what they consider key concerns for the church. Observers will be analyzing the remarks for clues as to how the cardinals will vote when they begin meeting April 18 to choose a new pope.

The network's leaders planned to distribute fliers in English and Italian around St. Peter's Square later today.

A spokeswoman for the U.S. Conference of Catholic Bishops declined comment. Law has also declined to comment through an aide at the Basilica of St. Mary Major in Rome, where the pope had appointed him archpriest last year. Law has apologized for his failures.

The Survivors Network, which claims hundreds of members, has spent more than a decade pressing U.S. bishops to acknowledge the scope of molestation in the church. They have picketed parishes, alerted the public to accused priests living in their communities and pressed authorities to prosecute bishops who failed to report abuse.

Some Catholics say the group is too strident and has close ties with lawyers making millions of dollars from suing the church.

But the Survivors Network says the overwhelming majority of its members have never sued and are too traumatized to do so. They say they adopted their tactics after bishops promised for years to take action against guilty clergy, then never did.

Some Boston Catholics said Law's role in mourning the pope was another sign that church officials did not understand the betrayal parishioners felt over his wrongdoing.

The abuse crisis erupted in 2002 with the case of one accused priest in Boston, then spread nationwide, compelling American bishops to enact sweeping reforms of their discipline policy for guilty priests.

According to studies the bishops commissioned to restore trust in their leadership, more than 11,000 abuse claims have been made against U.S. clergy since 1950. The total payout to victims has climbed to at least $840 million.

The Vatican, meanwhile, released video today to give outsiders a peek at the conclave where a new pope will be selected by the 115 cardinals who are under age 80 and thus eligible to vote.