A group of Catholic activists opposed to clergy sex abuse is demanding Washington Archbishop Donald W. Wuerl intervene to prevent a Vatican official from celebrating a high Latin Mass this weekend at the National Shrine of the Immaculate Conception.

"This is the wrong man sending the wrong message at the wrong time," said David Clohessy, executive director for the Survivors Network of those Abused by Priests (SNAP).

The upcoming Mass, whose planners are terming as a "historic" event, will be the first Tridentine rite celebrated in half a century from the Shrine's high altar. Slated for 1 p.m. Saturday, it will include three choirs, about three dozen priests and a small army of deacons and acolytes. Thousands of worshippers are expected to pack the 3,500-seat church for the Mass, which will commemorate Pope Benedict XVI's fifth year in the pontificate.

But its chief celebrant, Cardinal Dario Castrilln Hoyos, 80, of Colombia, was exposed last week for lauding in a 2001 letter a French bishop for refusing to denounce a priest-rapist.

The letter is the latest of a long string of recent embarrassments for the Vatican on its handling of the clergy sex abuse crisis in Europe. Once its contents were divulged Thursday by a French website, the Vatican quickly scrambled to defend Cardinal Hoyos, who oversaw the Vatican's Congregation for the Clergy from 1996 until 2006, when he retired.

And over the weekend, Cardinal Hoyos defended himself during a speech in the Spanish city of Murcia, saying he ran the letter by Pope John Paul II before sending it.

Dated Sept. 8, 2001, the missive to French Bishop Pierre Pican of Bayeux-Lisieux is about a local priest the Rev. Rene Bissey in that section of Normandy. The bishop kept Father Bissey in parish work even though the priest had admitted he was a pedophile.

The bishop later said he did not tell police about the perpetrator because he was obliged to keep the seal of the confessional. According to news reports, the bishop also had been informed about the abuse outside the confessional by the mother of one of the victims.

The priest was later sentenced to 18 years in jail for repeated rape of a boy and sexual assaults on 10 other young men.

Bishop Pican received a suspended three-month jail sentence for not immediately suspending the priest. The 2001 verdict against him was the first time in France that a bishop had been convicted for failing to disclose sexual abuse of minors by