PHILADELPHIA -- Pope Francis began his day in Philadelphia Sunday by forcefully condemning clerical sex abuse and meeting with several victims.

The problem of abuse and how to deal with it has plagued the church for decades.

Before his scheduled speech Sunday to a conference of bishops St. Martin's Chapel, the pope made an unscheduled stop to meet with five people who suffered sexual abuse as minors at the hands of clergy, family members or teachers.

Then, speaking at the conference, Francis delivered a strong message, promising to hold those responsible accountable, including anyone who may have covered up for predators.

"I have to, In my heart, these stories of suffering, of those youth that were sexually abused, and it continues to be on my mind that people who had the responsibility to take care of these tender ones violated that trust and caused them great pain. God weeps," Pope Francis said.

The Vatican said during his meeting with victims, the pope listened to their stories, prayed and expressed his shame in those priests involved.