Catalonia will hold a referendum on October 1 on whether to leave Spain, the head of the region announced Friday.
"The question will be: 'Do you want Catalonia to become an independent state in the form of a republic'," said Carles Puigdemont, the head of the regional government, Reuters reports.
But the Spanish government said the vote will not happen.
"That referendum will not take place because it is illegal," government spokesman Inigo Mendez de Vigo told a news conference, according to Reuters. "This is just another strategic step that doesn't lead anywhere."
Madrid has the power to intervene in Catalonia's regional government and cancel the vote, under Article 155 of Spain's constitution, but as Reuters explains, that's seen as a move of last resort. More likely, says the news wire, is months of legal wrangling and possibly fresh elections in Catalonia.
The region held an independence vote in November 2014, and it passed overwhelmingly. But as NPR's Lauren Frayer reported then, the vote was largely symbolic, and Madrid did not recognize the results:
"Spain had ordered the voting halted, and there were fears that the Spanish government might send Civil Guard troops to try to block polling stations. But voting went off peacefully, with some 2.25 million people casting ballots.
"Initial results show nearly 81 percent of voters marked 'yes, yes' on the two-question ballot, which asked: "Do you want Catalonia to be a state? If so, do you want that state to be independent?"
"But turnout was low, at least compared with Scotland's independence referendum back in September, in which more than 85 percent of residents participated. In Catalonia, less than half of eligible voters cast ballots, in a region of 7.5 million."
Part of the battle for separatists will be making the case that Catalonia would be better off on its own. The region accounts for almost one-fifth of Spain's economy, and has a population of 7.5 million.
"I believe in the right to vote — but with regards to independence, no one has ever really convinced me of the benefits," Antonio Piera told Reuters as he waited for a bus in central Barcelona.
Prime Minister Mariano Rajoy says that Catalonia would have to reapply to join the European Union, and also would lose up to 30 percent of its GDP, according to the Associated Press.
Earlier this year, the Spanish government barred from office some of the politicians who had been involved in setting up the vote in 2014, including Artur Mas, the region's former president.
The AP reports the latest polls show that a majority of people in Catalonia support holding a referendum, but far fewer support actually separating from Spain: just 44.3 percent support a split.
In 2015, former FC Barcelona star and current Manchester City manager Pep Guardiola lent his support to the independence cause, agreeing to stand as a candidate for separatist parties. Guardiola is expected to speak Sunday at a march in Barcelona in support of the vote.
Catalonia's independence movement has drawn comparisons with the separatist movement in Scotland. But with the Scottish National Party losing more than 20 seats in the U.K.'s election Thursday, a second vote on Scottish independence is now less likely.