Pope Benedict XVI told America's Roman Catholic leaders Wednesday evening that the clergy sex abuse scandal has sometimes been "very badly handled," his harshest criticism yet regarding the crisis that has badly damaged the U.S. church.

Benedict's remarks came at a prayer service with hundreds of American bishops at a national shrine in Washington, and marked the second time the pope has addressed sex abuse on his first papal journey to the U.S.

On his flight from Rome, the pope said he was deeply ashamed of the scandal and would fight to keep pedophiles out of the priesthood.

Benedict addressed clerical molesters in the wider context of secularism and the over-sexualization of America. "What does it mean to speak of child protection when pornography and violence can be viewed in so many homes through media widely available today?" he asked.

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The pope spoke after Cardinal Francis George of Chicago, who is the president of the U.S. Conference of Catholic Bishops.

George said that the consequences of the clergy abuse scandal "and of its being sometimes very badly handled by bishops makes both the personal faith of some Catholics and the public life of the church herself more problematic."

Benedict seemed to agree with that assessment.

"Responding to this situation has not been easy and, as the president of your episcopal conference has indicated, it was sometimes very badly handled," he said.

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Benedict said that it was important to remember that the vast majority of priests served faithfully but that it also was the bishops' "God-given responsibility" to reach out to those who had been "so seriously wronged."

Earlier in the day, Benedict drew an adoring crowd of 13,500 people to the South Lawn, where his 81st birthday was celebrated with President Bush — complete with choruses of "Happy Birthday" and a big cake.

The warm feelings didn't stop the pope from gently nudging the U.S. in a White House speech to use diplomacy to resolve international disputes. And differences on other issues also were apparent.

"America has traditionally shown herself generous in meeting immediate human needs, fostering development and offering relief to the victims of natural catastrophes," the pope said. "I am confident that this concern for the greater human family will continue to find expression in support for the patient efforts of international diplomacy to resolve conflicts and promote progress."

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Benedict and President Bush spoke alone in the Oval Office for 45 minutes after the ceremony, and a joint statement said the two "reaffirmed their total rejection of terrorism as well as the manipulation of religion to justify immoral and violent acts against innocents."

It also said the leaders "touched on the need to confront terrorism with appropriate means that respect the human person and his or her rights," a reference White House press secretary Dana Perino could not explain.

Benedict has been critical of harsh interrogation methods, telling a meeting of the Vatican's office for social justice last September that, while a country has an obligation to keep its citizens safe, prisoners must never be demeaned or tortured.

On Iraq, the discussion steered away from the war itself to focus primarily on worries for the Christian minority in the Muslim-majority country, Perino said. Other topics included human rights, religious freedom, fighting poverty and disease in Africa, the Israeli-Palestinian dispute, Lebanon and terrorism.

Wednesday's session marked the 25th meeting between a Roman Catholic pope and a U.S. president, conferences that have spanned 89 years, five pontiffs and 11 American leaders.