O'Neill has also insisted Villa have not received a new bid from Liverpool for the England midfielder, who will not be present when Villa report back for pre-season training at Bodymoor Heath on Thursday.
Liverpool were linked with a new £15million offer for 27-year-old Barry but O'Neill said: "There is no truth in this morning's reports and the situation remains the same.
"Gareth will not be returning to training tomorrow and he has been disciplined after giving an unauthorised interview to the News of the World."
A club statement confirmed: "Gareth Barry will not be returning for pre-season training tomorrow (Thursday)."
Barry upset O'Neill by suggesting the Villa boss was more interested in being a TV pundit for the Euro 2008 finals than speaking to him over his future.
O'Neill, despite being resigned to losing Barry, is adamant he will not accept less than £18million.