Celtic will have to wait until Friday before UEFA's disciplinary body meet to discuss accusations of "illicit chanting" during the Hoops' home win over Rennes on November 3.
The Parkhead club were expecting the complaint, made by the Strathclyde Police match commander to the UEFA match delegate following the Europa League Group I game, to be addressed on Thursday.
However, UEFA have an appeals body meeting scheduled to take place which means Celtic's case, among others, has been put back 24 hours.
Celtic were told on Monday that they had escaped Scottish Premier League action over pro-IRA chanting at their clash with Hibernian on October 29.
The SPL ruled that the Parkhead club had taken all reasonable action to prevent such "unacceptable conduct", which was reported by police. SPL secretary Iain Blair only confirmed Celtic were under investigation when questioned on the issue after the UEFA action became public.