VATICAN CITY » Pope Benedict XVI accepted the resignation of Philadelphia archbishop Cardinal Justin Rigali on Tuesday, sending him into retirement as the archdiocese faces accusations that it covered up a long-running priest sex abuse scandal.

The pope named Denver Archbishop Charles Chaput, of the U.S. bishops conservative wing, to succeed him.

The brief Vatican announcement said the resignation of the 76-year-old Rigali was because of his age. He submitted it on his 75th birthday in April 2010, as required by church law, but the pope did not immediately act on it.

Rigali has been under pressure for his handling of the scandal. A 2005 grand jury report charged that he and his predecessor hid credible sex-abuse complaints made against dozens of Philadelphia priests.

After eight years under Rigali’s leadership, the archdiocese is defending unprecedented criminal charges filed against a former secretary of clergy for allegedly transferring pedophile priests without warning new parishes.

Earrlier this year, the head of the archdiocese’s lay review panel on abuse, Ana Maria Catanzaro, said Rigali and his bishops "failed miserably at being open and transparent" when dealing with accused priests.

The scandal has surfaced twice during his tenure as head of the archdiocese of nearly 1.5 million people.

The Philadelphia grand jury that recommended the criminal charges this year faulted Rigali for keeping many area priests in active ministry despite credible allegations of sexual abuse. And a 2005 grand jury report charged that Rigali and his predecessor hid credible sex-abuse complaints made against dozens of Philadelphia priests.

The archdiocese called the first report "a vile, mean-spirited diatribe," though Rigali apologized to victims in a letter to parishioners.

Rigali, a former archbishop of St. Louis, spent three decades as a Vatican diplomat and high-level administrator and has kept his close contacts in Rome.

Chaput, 66, is known as an outspoken U.S. bishop who has criticized Catholic politicians who support abortion rights, speaks out against government playing too big a role in health care and opposes gay marriage and stem-cell research.

In 2010, he defended a decision by a Catholic school in Colorado not to re-enroll two children of a lesbian couple. Chaput said the parents of Catholic school students are expected to agree with church beliefs, including those forbidding sex between anyone other than married, heterosexual couples.

Chaput was one of the bishops Benedict chose in 2009 to investigate the Legionaries of Christ, the disgraced religious order that in recent years confirmed that its late founder fathered three children and sexually abused young seminarians. The pope also turned to Chaput in another sensitive case: an inquiry into Australian Bishop William Morris of the Toowoomba diocese, who Benedict removed in May partly because the bishop indicated he would ordain women and married men if church rules allowed the practice.

Between 2005 and 2008, the archdiocese of Denver settled 43 sex abuse allegations against priests for a total of $8.2 million. Chaput has publicly apologized to all the victims, sating the church was "mortified and embarrassed."

"It’s obvious Rome is asking Archbishop Chaput to handle several very tough and sensitive jobs," said Russell Shaw, a former spokesman for the U.S. Conference of Catholic Bishops who is friendly with Chaput. "He was regarded in Rome already as a very able and reliable man who could be counted on to do a good honest job and do it well."

In Philadelphia, Rigali has overseen the closing of dozens of Catholic schools because of declining enrollment, but he also spearheaded the construction of two suburban high schools and a church for a burgeoning immigrant Hispanic community.

AP correspondent Alessandra Rizzo contributed from the Vatican.