The Spanish government on Monday rolled out a legal roadblock to stop the Catalonia region voting on independence, branding the planned ballot an affront to the sovereignty of Spain.
After Catalonia's president Artur Mas staked his leadership on the issue by calling the vote for November 9, the national government responded by filing a constitutional challenge.
Conservative Prime Minister Mariano Rajoy said he "deeply" regretted Mas's move, saying it "divides Catalans, alienates them from Europe and the rest of Spain and seriously harms their welfare".
He said the government had sent the appeal to the Constitutional Court and that Mas's measures would be suspended as soon as that tribunal accepted the appeal, pending a final decision by its judges.
Buoyed by mass street demonstrations, Mas has pushed ahead for a vote in defiance of Rajoy's warnings.
Since he signed a decree on Saturday calling the vote, a luminous clock on Barcelona's historic Sant Jaume square has been ticking down the seconds to November 9.
Pro-independence Catalans celebrate in Barcelona after the signing of a regional law to vote on inde …
"You cannot use the law to prevent people indefinitely from stating their opinion," Mas said in a television interview on Sunday in anticipation of Monday's appeal.
"Voting on November is the best thing for everyone because it will allow us and also the Spanish government to know what the Catalan people's opinion is."
Rajoy retorted on Monday that the right to decide on a region's status belonged to "all of the Spanish people" under the country's 1978 constitution -- the keystone of Spain's democracy after the death of the dictator Francisco Franco.
"There is nothing and no one, no power nor institution, that can break this principle of sole sovereignty," Rajoy told reporters after an extraordinary cabinet meeting.
- Catalans defiant -
President of Catalonia's regional government Artur Mas delivers a speech after signing a regiona …
The appeal did not put off supporters of independence, who vowed to continue preparing for the vote, setting up a tense standoff over the coming weeks.
"We are committed to voting on November 9," said Oriol Junqueras, leader of the left-wing Catalan nationalist party ERC, which is allied with Mas's conservative CiU grouping in the regional parliament.
"We are aware of the great difficulties we will face in the coming days but we are ready to face those difficulties."
Fired up by Scotland's independence referendum earlier this month, vast crowds turned out in Barcelona on September 11 to demand their own vote.
Scottish voters eventually chose not to be independent from Britain.
Pro-independence Catalans hold a flag reading "We are a nation" as they rally in Barcelona …
But like Scotland, Catalonia "wants to be heard and it wants to vote," Mas said.
Mas has vowed to let Catalans vote on independence but has also promised to respect Spanish law.
He has hinted that if the government blocks the vote, he could put his leadership at stake in an early regional election, which could serve as a plebiscite on the issue.
Catalonia is Spain's economic powerhouse, accounting for about a fifth of the country's economy. But like the rest of Spain, it suffered from the 2008 property crash and resulting economic downturn.
Proud of their Catalan language and culture, many of the region's 7.5 million inhabitants feel short-changed by the government in Madrid which redistributes their taxes.
The independence movement in Catalonia has gathered strength in recent years as Spain's economic crisis has increased unemployment and hardship in the region and swelled its debts.
Catalonia formally adopted the status of a "nation" in 2006 but the Constitutional Court overruled that claim.
The main opposition Socialist Party is calling for a constitutional reform instead of a vote to answer Catalan demands for greater autonomy.
The Socialists' leader Pedro Sanchez on Monday said the referendum plan "deeply damages Spanish democracy".