La Liga said the rules state postponed games should be played at the earliest possible opportunity, which is 4 December, and that clubs have no power to decide dates of matches.
LaLiga: Barcelona vs Real Madrid 'El Clasico' to be played on 18 December, says Spanish federation; league unhappy with new date
The rearranged Clasico between Barcelona and Real Madrid will be played on 18 December despite opposition from La Liga, the Spanish Football Federation (RFEF) confirmed on Wednesday.
Barcelona coach Ernesto Valverde calls for 'common sense' for swift resolution to El Clasico scheduling problem
Valverde was speaking ahead of Barcelona's Champions League game away at Slavia Prague on Wednesday, when his team will have the chance to go top of Group F.
LaLiga: El Clasico postponed due to Catalonia protests; Real Madrid, Barcelona told to find new date
The clubs have until 10:00 am (0800 GMT) on Monday to find a new date for Clasico, which will be decided by the RFEF if the clubs cannot reach an agreement.