The president of Spain's Catalonia region, Artur Mas, has signed a decree calling an independence referendum on November 9.
In reaction, the Spanish government said Catalonia would not be allowed to hold the referendum.
Deputy Prime Minister Soraya Saenz de Santamaria told a news conference on September 27 that no one is "above the national will of all Spaniards," calling the referendum "unconstitutional."
Saenz de Santamaria said the Spanish government will hold an emergency cabinet meeting within days so the referendum can be challenged before Spain's Constitutional Court.
Pro-independence sentiment in the economically strong region has surged in recent years, fueled by a sense that the region deserves better fiscal and political treatment from Madrid.