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 said 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.
A report on BBC says the Catalan parliament will meet on Thursday to decide on its response.
The pro-independence leaders could decide to formalise a unilateral declaration of independence.
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, 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 radio programme, 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?
"Because what I can tell you is that the people and the institutions in Catalonia will not let this happen."
He said the Spanish government needed to recognise that the people of the region had voted for independence.
The Catalan government said that of the 43 per cent who took part in the 1 October referendum, 90 per cent were in favour of independence.
Unionist parties who won about 40 per cent of the vote at the 2015 Catalan elections boycotted the ballot and many anti-independence supporters stayed away, arguing it was not valid.