Barca and Madrid must now agree to a new date by 10:00 CEST on Monday October 24.
Should the two clubs fail to reach an agreement, the Spanish FA's Competition Committee will determine the date.
The Clasico promised to be a particularly fraught one due to the two clubs' respective positions on the Spanish political spectrum. Barcelona have long been associated with Catalan independence, with the colours of the Senyera, the Catalan flag, featuring prominently in the club's crest.
Meanwhile, several current and former players have expressed their support for secession, most notably Gerard Pique and Pep Guardiola. Barca had released a statement in support of the jailed pro-independence leaders.
Real Madrid, meanwhile, are associated with the other end of the Spanish political spectrum, with the dictator Franco seeking to align himself with the club during their successful spell in European football in the 1950s. During the Spanish civil war, Francoist troops arrested Barcelona president Josep Sunyol.