(CNN) Pope Francis has apologized for making comments he said were hurtful to victims of clerical sex abuse.

The pontiff sparked controversy when he defended embattled Chilean Bishop Juan Barros -- who is accused of covering up sex abuse by his mentor Father Fernando Karadima.

According to Crux, a Catholic news outlet, the Vatican found Karadima guilty of sexual abuse in 2011 and sentenced him to a life of prayer and penitence. Barros has denied allegations that he covered up the abuse.

In the port city of Iquique, Chile, his last stop before heading to Peru, Francis defended Barros, telling reporters Thursday that the accusations amounted to slander, according to BioBioChile radio. "The day they bring me proof against Bishop Barros, that's the day when I'll talk," he said

"There is not a single proof against him, everything is slander."

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