MADRID — Spanish authorities gave Catalonia’s separatist leader five days to explain whether his ambiguous statement on secession was a formal declaration of independence and warned Wednesday that his answer dictated whether they would apply never-used constitutional powers to curtail the region’s autonomy.

Threatening to invoke a section of the Spanish Constitution to assert control over the country’s rogue region, Prime Minister Mariano Rajoy said Catalan president Carles Puigdemont’s response to the central government’s ultimatum would be crucial in deciding “events over the coming days.”

Puigdemont announced on Tuesday that he was using the victory in a banned Oct. 1 referendum to proceed with a declaration of Catalan independence, but proposed freezing its implementation for a few weeks to allow for dialogue and mediation with the government in Madrid.

Speaking Wednesday, Rajoy said the referendum Catalonia’s regional parliament and Puigdemont’s government held in violation of a court order was illegal and part of a strategy “to impose independence that few want and is good for nobody.”

Lawyers, civil society groups and politicians in Catalonia and elsewhere in Spain have offered to mediate between the two sides, but the prime minister rejected the offers.