Pope Francis met with victims of child sexual abuse Sunday on the final day of his U.S. visit and promised to hold accountable those responsible for the scandal in the church, delivering a powerful warning to American bishops accused of covering up for pedophile priests instead of reporting them to police.

In a gesture of reconciliation just hours before he was to return to Rome, the pope told the victims he is “deeply sorry” for all the times they came forward to report the abuse and weren't believed. He assured them that he believes them.

“I pledge to you that we will follow the path of truth wherever it may lead,” Francis said in Spanish while in the City of Brotherly Love for a big festival on the Catholic family. “Clergy and bishops will be held accountable when they abuse or fail to protect children.”

It was Francis’ second such meeting: He received sexual abuse victims at the Vatican in July 2014.

But in an apparent effort by the church to reshape the discussion, the Vatican said not all five of the victims on Sunday were abused by members of the clergy; some of the three women and two men had been victimised by relatives or educators.

Later Sunday, Francis visited a Philadelphia jail to give hope and encouragement to about 100 inmates, included suspected killers, rapists and mobsters.

In the afternoon, the pope was scheduled to celebrate a final Mass on U.S. soil on Philadelphia’s grandest boulevard, the Benjamin Franklin Parkway, with organisers predicting a crowd of 1 million.

It was expected to be the biggest event of his six-day U.S. trip, a triumphant whirlwind journey that also took him to Washington and New York, where he drew large and adoring crowds, met with President Barack Obama, visited ground zero and addressed Congress and the United Nations, calling for urgent action on climate change and poverty.

The Archdiocese of Philadelphia has been hit hard by the sexual abuse scandal and has been the subject of repeated grand jury investigations, including one that accused it keeping on assignment more than three dozen priests facing serious accusations. A monsignor was found guilty of endangering children by not removing pedophile priests, becoming the first American church official convicted of such an offense.

The pope has agreed to create a new Vatican tribunal to prosecute bishops who failed to protect their flock, and he has accepted the resignations of three U.S. bishops accused of mishandling cases. During the previous meeting with victims, he similarly vowed to hold bishops accountable.

At the same time, Francis and U.S. bishops have also argued that child molestation is a serious problem beyond the church, especially within families and in schools. The meeting with victims abused by people other than priests underscored that point.

Victim support groups were unimpressed by Sunday’s meeting, which took place a day after the pope celebrated Mass with Cardinal Justin Rigali, who was the leader of the Philadelphia archdiocese when it was accused of sheltering pedophiles.

The main victims’ support group, SNAP, dismissed the meeting as an exercise in public relations.

SNAP’s David Clohessy said, “Is a child anywhere on earth safer now that a pope, for maybe the seventh or eighth time or ninth time, has briefly chatted with abuse victims? No.”

The Rev. Tom Doyle, a canon lawyer who worked at the Vatican embassy in Washington and is now an advocate for victims, said that including more than just victims of abusive clergy “seriously minimises” the problem in the church.

“We don’t think we’re going to get any real support to change this from the leadership in the Vatican,” Doyle said in a phone interview. “They’re having this big meeting of families. But there’s been no real room for all the families that the Catholic Church has destroyed through sexual abuse.”

The Vatican spokesman, the Rev. Federico Lombardi, said the pope met with the victims for more than a half-hour at the St. Charles Borromeo seminary. He said the pope prayed with them, listened to their stories and expressed his closeness in their suffering and his “pain and shame” in the case of those abused by priests.

Separately, the pope met with American bishops in town for the family festival and repeated to them face-to-face his vow to hold them accountable for their misdeeds. (AP)

•Photo shows Pope Francis.