Spain's deputy prime minister Soraya Saenz de Santamaria has said that Catalonia's leader Carles Puigdemont did not provide an adequate response in his letter clarifying the region's status.
Ms Saenz de Santamaria said Catalonia's leader has until Thursday to return to adhering to Spain's laws.
Earlier Catalan leader Carles Puigdemont called for dialogue with Madrid and a meeting with the country's prime minister
But the letter, released about two hours before the deadline was set to expire, did not clarify whether he indeed had proclaimed that Catalonia had broken away from Spain.
The central government had explicitly asked him to respond with a simple "yes" or "no" to that question.
Instead, Mr Puigdemont replied with a four-page letter seeking two months of negotiations and mediation.
"The priority of my government is to intensively seek a path to dialogue," Mr Puigdemont said in his letter.
"We want to talk ... Our proposal for dialogue is sincere and honest."
Spain has repeatedly said that it is not willing to sit down with Mr Puigdemont if calls for independence are on the table, or accept any form of international mediation.
Prime Minister Mariano Rajoy's government has threatened to activate Article 155 of Spain's constitution, which could see Madrid take temporary control of some parts of Catalonia's self-government.
Meanwhile a Spanish prosecutor is asking for Catalonia's regional police chief to be jailed in a sedition case related to the staging of Catalonia's banned October 1 secession referendum.
Major Josep Lluis Trapero gave evidence for about two hours at Madrid's National Court on Monday, following which the court prosecutor recommended he be sent to prison provisionally without bail.
Maj Trapero, another regional police offer and the leaders of two pro-independence associations are under investigation for sedition for their roles in September 20-21 demonstrations in Barcelona as Spanish police arrested several Catalan officials and raided offices in a crackdown on referendum preparations.
