Pope Francis apologised for comments he made about victims of paedophile clergy during his trip to South America, but repeated his defence of a bishop accused of protecting a predatory priest.
The Pope issued the partial mea culpa on board the plane that flew him back to Rome after a grueling week-long trip to Chile and Peru.
During his visit to Chile, he had insisted that there was no evidence that Bishop Juan Barros was complicit in keeping quiet about the sexual abuse carried out by a priest, the Rev. Fernando Karadima.
The Pope sharply told journalists: "The day I see proof against Bishop Barros, then I will talk. There is not a single piece of evidence against him. It is all slander. Is that clear?"
On the plane home he acknowledged that his remarks had upset many victims of clerical abuse and caused huge controversy during his trip.
"Here I have to apologise because the word 'proof' hurt them. It hurt a lot of abused people," he said. "I know how much they suffer. And to hear that the Pope told them to their face that they need to bring a letter with proof? It's a slap in the face."
But he repeated that anyone who makes such accusations without providing evidence is guilty of slander.
He insisted that to date no one had provided him with evidence that Bishop Juan Barros was complicit in keeping quiet about the perversions of the Rev. Fernando Karadima, a Chilean priest who was sanctioned by the Vatican in 2011 for molesting and fondling minors in his Santiago parish.
The pontiff's original remarks were widely condemned in Chile and revived questions about whether he "gets it" about sex abuse.
On the flight back to Rome, he insisted that Barros would remain bishop of Osorno, Chile, as long as there's no evidence implicating him in the cover-up.
"I can't condemn him because I don't have evidence," Francis said. "But I'm also convinced that he's innocent."
Karadima was removed from ministry and sentenced by the Vatican in 2011 to a lifetime of penance and prayer based on the testimony of his victims.
A Chilean judge also found the victims to be credible, saying that while she had to drop charges against Karadima because too much time had passed, proof of his crimes wasn't lacking.
The victims have said for years that Barros witnessed the abuse and did nothing to stop it. Barros denies the accusations.