Spanish Prime Minister Mariano Rajoy has given Catalonia’s separatist leader five days to say whether or not he has declared independence.
If Carles Puigdemont confirms by Monday that he has, he will be given a further three days to withdraw the declaration.
Failing that, Madrid will invoke Article 155 of the constitution allowing it to suspend the region’s autonomy and impose direct rule.
BBC reports that the Catalan leaders signed a declaration of independence on Tuesday.
However, they halted its implementation to allow for talks with Madrid.
Spain has been in turmoil since the separatist government held a disputed referendum in Catalonia on 1 October which was declared invalid by the country’s Constitutional Court.
Almost 90% of voters backed independence with a turnout of 43%, Catalan officials say. Anti-independence voters largely boycotted the ballot and there were several reports of irregularities.
National police were involved in violent scenes as they tried to stop the vote taking place.
Mr Rajoy said his government had asked the regional government to clarify whether or not it had declared independence.
He accused Mr Puigdemont of having created “deliberate confusion” and said he wanted to restore “certainty”.
“This call – ahead of any of the measures that the government may adopt under Article 155 of our constitution – seeks to offer citizens the clarity and security that a question of such importance requires,” Mr Rajoy said.
“There is an urgent need to put an end to the situation that Catalonia is going through – to return it to safety, tranquillity and calm and to do that as quickly as possible.”
Mr Rajoy was speaking after holding an emergency cabinet meeting on Wednesday morning to discuss the government’s next steps.
Speaking later in parliament, Mr Rajoy said Spain was facing the most serious threat to its 40-year-old democracy.
He accused the separatists of hatching an “anti-democratic plan foisting their will on all the people of Catalonia”, and said the Spanish government had had no choice but to restore order.
“It falls to the Catalan leader to restore constitutional normality,” he told deputies, rejecting any suggestion of outside mediation in the dispute.
He added that he was willing to negotiate on the issue of regional autonomy and changes to the constitution – but this had to be within the framework of the law