ROME (Reuters) - A coalition of Catholic groups and victims of abuse by clergy unveiled a report Tuesday that accused the Vatican of trying to hide widespread child sex abuse scandals and called on the United Nations to step in.

"There has been cover-up and collusion not only on the part of the bishops but by the Vatican," said Frances Kissling, president of U.S.-based Catholics for a Free Choice, which spearheaded the research.

"This report shows that sexual abuse in the Catholic church is not an American crisis, it is a global crisis," she said.

The group plans to present its report, highlighting 5,000 alleged cases of abuse by members of the clergy worldwide, to the U.N. Committee on the Rights of the Child Wednesday.

"We urge the Committee to take up the serious task of calling the Holy See to account for perpetrating and perpetuating the crisis," the report says.

The delegation stopped in Rome Tuesday to push for talks with the Holy See and present their report to the Vatican press.

The launch of the 40-page document comes as the Vatican prepares to release its official response to rules adopted in June by U.S. bishops to deal with pedophile priests.

U.S. CRISIS

The worst crisis ever to hit the American Catholic Church exploded in January when documents revealed that the Boston Archdiocese reassigned priests accused of molesting children. The scandal spread and led to the dismissal of some 300 priests.

The new rules say a bishop should dismiss a cleric "of any ecclesiastical ministry or function" if there is a "credible" accusation that a priest sexually abused a minor.

The leaders of the U.S. Roman Catholic bishops will visit the Vatican next week for talks centered on the scandals.

Pope John Paul called U.S. Church leaders to the Vatican for an unprecedented summit in April where he made clear there was no room in the ministry for sex offenders. However, the Vatican is worried the crisis could spark a witch hunt.

Critics say the Holy See is not doing enough.

"If I committed a crime I could write a letter to myself and say: 'I'm sorry, I won't do it again' but I've still got to face governmental and other authorities to deal with the consequences of my actions," said Mark Furnish, a New York attorney who was sexually abused by a priest when he was 12.

The report says 5,000 cases of abuse by Catholic clergy in 20 different countries have been reported in the media since 1995, with some of the allegations referring to incidents as long ago as the 1940s.

The group wants the United Nations to request a full report from the Vatican outlining the problem.

Kissling said the United Nations should consider sanctions if the Holy See fails to resolve the crisis.

A solution would mean bringing an end to sex abuse by clergy, the group said, as well as removing bishops who have transferred offending priests rather than defrocking them and ending what it sees as a policy of secrecy.

The coalition also demanded that the Pope himself apologize to the victims for the abuse