Pope Benedict XVI has begged forgiveness from clerical abuse victims and promised to "do everything possible" to ensure priests don't rape and molest children ever again.

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Priests pray in St. Peter's Square at the Vatican on June 10. Pope Benedict XVI led an evening vigil service to celebrate the end of the church's Year of the Priest. ((Pier Paolo Cito/Associated Press))

Benedict made the pledge during a Mass Friday in St. Peter's Square, marking the end of the Vatican's Year of the Priest, a celebration of the priesthood that has been marred by revelations of hundreds of new cases of clerical abuse, coverup and Vatican inaction to root out pedophiles.

In his homily, Benedict lamented that during what should have been a year of joy for the priesthood the "sins of priests came to light, particularly the abuse of the little ones."

He said the scandal was a call for purification of the church.

Celebrates celibacy

On Thursday, Benedict strongly defended celibacy for priests as a sign of faith in an increasingly secular world, insisting on a church tradition that has come under scrutiny amid the clerical sex abuse scandal.

He made the comments to some 15,000 priests who massed in St. Peter's Square during an evening vigil service to mark the end of Year of the Priest.  

Benedict responded to preselected questions from five priests and none asked for his thoughts about the abuse scandal. But one asked him to speak instead about what he called the "beauty of celibacy," which he said was so often criticized in the secular world.

The pope called it "a great sign of faith, of the presence of God in the world."

The Vatican has long denied that its celibacy requirement was the root cause of priests who rape and sodomize children. Yet the requirement — which is a tradition in the church but is not part of church doctrine — has come under increasing questioning amid the scandal, and even some top prelates have called for an honest examination of it.