But he continued to defend Chilean bishop Juan Barros, who is accused by victims of covering up for the country's most notorious paedophile priest.
He also repeated that anyone who makes such accusations without providing evidence is guilty of slander.
Francis said: "I can't condemn him because I don't have evidence. But I'm also convinced that he's innocent."
Francis issued the partial mea culpa in an airborne press conference as he returned home from South America, where the scandal plunged the Chilean church into renewed crisis and revived questions about whether Francis "gets it" about abuse.
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