BBC: Pope Benedict XVI has been celebrating an open-air Mass at the Nationals stadium in Washington DC in front of more than 40,000 people.
This is the first such event organised for the Pope's six-day visit to the United States.
He spoke of the sexual abuse of children by Roman Catholic clergy in the US, saying no words of his could describe the pain and harm inflicted.
Later, the Pope will hold an inter-faith meeting.
On the subject of child abuse, he said: "No words of mine can describe the pain and the harm inflicted by the sexual abuse of minors.
"It is important that those who have suffered be given loving pastoral attention. Nor can I adequately describe the damage that has occurred within the community of the Church."
Efforts to protect children must continue, he said.
For the third time in as many days, he has done what many Catholics have been asking for years - he has condemned and publicly accepted full responsibility for the crimes of sexual abuse committed by Catholic priests in the United States, says the BBC's David Willey who is travelling with the Pope during his visit.
Many members of the congregation were immigrants from various countries in central and South America and they cheered the Pope wildly when he added some remarks in fluent Spanish, praising the vitality of their Christian faith. Thousands Attend Pope's US Mass >>>
The Dawning of a New Dark Age (Paperback - UK)
The Dawning of a New Dark Age (Hardback - UK)
