Spanish Prime Minister Mariano Rajoy has threatened to remove Catalonia's regional autonomy after an emergency cabinet meeting to discuss how to respond to Catalan separatists signing an independence declaration.
In a televised address, he asked the Catalan President Carles Puigdemont to clarify whether independence had already been declared - before the Spanish government decides how to react.
Mr Puigdemont has insisted Catalans have earned the right to independence but that separatists would delay implementing it for several weeks to give dialogue with Madrid a chance.
But Spain's Deputy Prime Minister Soraya Saenz de Santamaria immediately rejected any notion of talks following a referendum which was deemed illegal, saying Mr Puigdemont "doesn't know where he is, where he is going and with whom he wants to go."
The cabinet is looking at a range of ways to deal with the separatist leaders and could include the "nuclear option" - suspending Catalonia's autonomy, taking over control of the region and sending in the national police.
The move would be a risk for Mr Rajoy, who for the first time in a veiled threat on Wednesday said clarity was "a requirement for any measure the government can adopt under Article 155 of the constitution."
It would allow Madrid to suspend the region's political institutions and impose its authority.
While there are those in Catalonia that oppose independence – they cling fiercely to their high degree of self-governance and would baulk at any interference from central government.
The brutality of the police response to the Catalan referendum came in for international criticism – and many Catalans would be strongly opposed to an increased national police presence.
Some 900 people were injured as police attempted to prevent people from casting their ballots in the October 1st vote.
However, Mr Rajoy will want to be seen to be sticking to his hard line against the independence movement.
He has decided to launch a constitutional reform, with the backing of Spain's opposition Socialist leader Pedro Sanchez, that could change the way the country's 17 autonomous regions are governed.
Mr Rajoy has not ruled out arresting Mr Puigdemont and other pro-independence figures – but again the move would risk adding fuel to the flame of the independence movement.
He has come under pressure to soften his stance on negotiations and European Council President Donald Tusk is among the latest to urge him to sit across the table from Mr Puigdemont.
The Catalan leader's speech last night seemed to be cast in overtures of compromise as he said separatists have nothing against Spain or Spaniards.
Mr Puigdemont added: "We're not criminals, we're not mad. We're normal people who want to vote."
Despite this, the signing of an independence declaration will be viewed by Madrid as an act of provocation and Mr Rajoy will struggle to find a way to respond that satisfies everyone.