Madrid (AFP) - Spain's leaders refuse to let their country break apart, but as Catalonia's independence drive gathers steam, analysts say Madrid may have to negotiate on a question affecting all of Europe.
Hundreds of thousands of nationalists demanding a vote on independence from Spain staged a mass demonstration in Barcelona on Thursday, gathering in red and yellow shirts to form a giant "V" for vote.
Nationalists and political experts alike said this raised the question of how long the Spanish government can resist without flinching, and how Europe would tackle a potential wave of secession demands.
"The problem is no longer just with Catalonia," said Fernando Vallespin, a political scientist at the Autonomous University of Madrid.
"The question of how you solve it depends not only on Spain but on the European Union. People are very worried about it."
Spain's constitution, approved by referendum in 1978 three years after the death of the dictator Francisco Franco, gave the country's regions a degree of autonomy, but not as much as some Catalans now want.
"Nearly 40 years have now passed and that agreement needs to be revised," said Anton Losada, a political scientist at Santiago de Compostela University.
"There is a real demand in society for a change in the structure of the Spanish state."
- Basque Country and beyond -
Thursday's demonstration in Catalonia was joined by sympathetic delegates from Spain's Basque Country. ETA militants waged an armed fight for independence there before declaring an end to it in 2010.
"Madrid must understand that the Catalans are not alone. We Basques are here, too," said Hasier Arraiz, leader of Sortu, one of a new generation of Basque parties seeking independence by political means.
"A 'no' to Catalonia would be a no to the Basque Country."
The Basque Country failed in its own bid to hold a referendum on the right to decide in 2008.
"They are watching the Catalan issue from a distance," said Florencio Dominguez, director of the Basque news agency Vasco Press.
"They have waged a strategy that seeks a reform of the state model, though not in a unilateral way like Catalonia is doing."
For its part, Catalonia formally declared itself a "nation" in 2006 but Spain's Constitutional Court later overruled that claim.
After that ruling, demands for a political settlement "became infectious and got worse," said Losada.
- Scotland holds the key -
Pro-independence Catalans are fired up by Scotland's independence referendum on September 18.
The region's nationalist president Artur Mas has called for Catalonia to hold its own vote on independence on November 9.
"The key to this is in Scotland," said Vallespin. "If the 'yes' vote wins in Scotland, that will break the taboo over secession in western Europe."
Spain's Prime Minister Mariano Rajoy says Catalonia cannot be compared to Scotland, where the British government has approved the referendum even though it opposes independence.
Rajoy has vowed to block the Catalan vote, but Mas said it is "impossible" to do so.
"This V is a very powerful message and very wide-reaching, and those in Madrid should listen to it," said Mas after Thursday's rally.
"The time has come for them to sit down and negotiate."
Whatever happens on November 9, something may budge in the standoff once that sensitive date is passed, Losada said.
The ruling Popular Party "has been gradually realising that something will have to be done with the constitution ... Now the question is how far-reaching to make that reform," he said.
"There is a real demand that requires a political response," he added. "Either you change, or you adapt, or it explodes."