Catalan authorities will not follow orders from the Spanish government if Madrid moves to reassert control over the region, a senior official says.
Foreign affairs spokesman Raul Romeva told the BBC the central government was acting against the will of Catalans.
Spain's Prime Minister Mariano Rajoy has announced plans to sack the region's government and curtail some of the freedoms of its parliament.
The Catalan parliament will meet on Thursday to decide on its response.
The Spanish Senate is expected to approve the government's measures on Friday along with a proposal for fresh regional elections.
How did we get here?
The Catalan government, led by President Carles Puigdemont, has refused to halt an independence drive following an outlawed referendum held earlier this month.
On Saturday, Mr Rajoy said he was triggering Article 155 of the constitution - an unprecedented move - which allows for direct rule to be imposed in a crisis on any of the country's autonomous regions.
But Catalan leaders say they will not accept the plan.
Speaking to BBC Radio 4's Today programme, Mr Romeva said: "How can the European Union live with that situation [if this happens]? How can the EU democracy survive and how can they be credible if they allow this to happen?