The Spanish government warned Catalonia's separatist leader on Tuesday not to do anything "irreversible", just hours before a possible declaration of independence from Madrid that could send shockwaves through Europe.
Whether or not Catalan president Carles Puigdemont will follow through on his threat to announce a full breakaway, defying the central government and Spanish courts, is still a mystery.
But the Spanish government issued a sharp warning to Puigdemont on Tuesday as it grapples with the nation's worst political crisis in a generation.
At stake is the future of a region of 7.5 million people deeply divided over independence, one of Spain's economic powerhouses whose drive to break away has raised concern for stability in the European Union.
We must be responsible and de-escalate tensions to protect social cohesion. Declaration on the current situation in Catalonia: pic.twitter.com/XGdnkaAL7U— Ada Colau (@AdaColau) October 10, 2017
Puigdemont, a 54-year-old former journalist and life-long independence advocate, will address Catalan lawmakers in an extraordinary parliamentary session beginning at 1600 GMT.
Political leaders in Catalonia, Spain and Europe have urged Puigdemont to stand down and ease the country's biggest upheaval since its transition to democracy in the 1970s.
But the Catalan president says an independence referendum that took place on October 1 despite a court ban ruling it unconstitutional justifies splitting from Madrid.
Catalan police were out in full force around the region's parliament in Barcelona ahead of Puidgemont's address.
"The end of the road," said Catalan daily El Periodico on its front page.
On Monday, Ada Colau, the popular mayor of Barcelona, warned that a unilateral declaration of independence would put "social cohesion" at risk.
The results of the referendum "cannot be an endorsement to proclaim independence but they constitute the possibility of opening a dialogue and international mediation", she said.
Madrid insists that any independence declaration would not change the legal reality that Catalonia is one of Spain's semi-autonomous regions with laws governed by the national constitution.
But EU nations are watching developments closely amid concern that Catalan independence could put further pressure on the bloc still dealing with the fallout from Britain's shock decision to leave.
After talks in Luxembourg with ministers from the European People's Party, the EU's right-of-centre political grouping, de Guindos said "everyone has supported the position of the Spanish government.”
"At 3 o'clock in Sydney, we will know if the world can get a new country when Catalonia reveals it will separate."pic.twitter.com/BJ3StL8XgY— Llibertat.cat (@Llibertatcat) October 10, 2017
Prime Minister Mariano Rajoy has vowed to use everything in his legal power to prevent Catalan independence and has even refused to rule out imposing direct rule over the region from Madrid, a move many fear could lead to unrest.
The crisis has caused deep uncertainty for businesses in one of Spain's wealthiest regions.
A string of companies have already moved their legal headquarters, but not their employees, from Catalonia to other parts of the country.
The head of Spain's chamber of commerce Jose Luis Bonet told Cadena SER radio that a unilateral independence declaration "would be a disaster".
"For Spain it would be extraordinarily negative and even for Europe it would mean enormous instability," Bonet said.