Spanish Prime Minister Mariano Rajoy said he would not rule out using constitutional powers to remove Catalonia's autonomous status if it claimed independence as tens of thousands took to the streets to call for talks.
The northeastern region of Catalonia, which has its own language and culture, held a referendum on 1 October on independence, in defiance of the Spanish constitutional court which had ruled the vote illegal.
Until now, Mr Rajoy has remained vague on whether he would use article 155, the so-called nuclear option, of the constitution which enables him to sack the regional government and call a fresh local election.
In an interview with Spanish newspaper El Pais Mr Rajoy was asked if he was ready to trigger the article 155 of the constitution, and said: "I don't rule out absolutely anything that is within the law... Ideally, it shouldn't be necessary to implement extreme solutions but for that not to happen things would have to be changed."