Pope Benedict then attended an evening ecumenical service with Protestant and Orthodox clergy at St Joseph's church in Manhattan.
Celebrating open-air Mass at the Nationals stadium in Washington DC on Thursday, the Pope spoke of the sexual abuse of children by US Catholic clergy before talking privately to a group of people who had been abused by priests.
The Pope, who was addressing 40,000 people, told the victims he would pray for them and their families.
He spent 25 minutes in individual meetings with half a dozen victims, some of whom were in tears during the encounters, a spokesman said.
During the open-air Mass, the pontiff said: "No words of mine can describe the pain and the harm inflicted by the sexual abuse of minors."
Efforts to protect children had to continue, he said.
Our correspondent says that for the third time in as many days, the pontiff 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 US.
On Wednesday, the pontiff met President George W Bush at the White House.
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