Pope Francis has met with victims of child-abusing priests on the final day of his US visit, and promised to hold those responsible for the scandal accountable as he delivered a powerful warning to American bishops accused of covering up for paedophiles instead of reporting them to police.
The pontiff disclosed the gesture of reconciliation at the start of a meeting with US bishops gathered in Philadelphia.
Pope Francis praised the victims as "true heralds of mercy" who deserve the church's gratitude, and said sex abuse in the church can no longer be kept a secret.
He promised to "zealously" protect young people and see that "all those responsible are held accountable".
Pope Francis has agreed to create a new Vatican tribunal to prosecute bishops who failed to protect their flock by covering up for paedophile priests.
Victims' advisory groups had complained earlier in the week that Pope Francis had neglected to address their plight when he congratulated bishops for their "courageous" and generous response to the scandal.
Today, he directed his attention to the victims in a city hit hard by the scandal. The Archdiocese of Philadelphia has been the subject of repeated grand jury investigations, and a monsignor was convicted of endangering children by not removing paedophile priests.
Later in the day, Pope Francis is scheduled to visit a prison and celebrate a final Mass on US soil on Philadelphia's grandest boulevard, the Benjamin Franklin Parkway.
Organisers say they expect one million people to turn out. But there are fears the extraordinary security - including airport-style bag searches, crowd-control cattle chutes and blocked-off streets - will scare away many.
At Curran-Fromhold Correctional Facility, Pope Francis plans to visit with 100 inmates, including suspected killers, rapists and mobsters. He is expected to offer them words of hope, forgiveness and redemption.
"His mission is the marginalised, the forgotten," prison spokeswoman Shawn Hawes said. "From our understanding, he wants those who are in custody to know that they are not forgotten and they can be redeemed."
Last night, Pope Francis was cheered by tens of thousands at a music-and-prayer festival on the Parkway, waving to the crowd in his open-air Pope mobile. Performers included Aretha Franklin and Andrea Bocelli.
He called families a "factory of hope", even with their imperfections.
"Defend the family, because that's where our future will play out," he said.