Speaking in Parliament, Mr Rajoy said Carles Puigdemont has until Monday at 10 am "to say if he declared independence" before suspending Catalan autonomy.
Prime Minister Mariano Rajoy has vowed to do everything in his power to prevent Catalan secession following a banned referendum in the region, which remains deeply divided over independence.
M - Spain is preparing to celebrate its National Day amid a continuing political crisis sparked by Catalonia's disputed independence referendum.
"The cabinet has agreed this morning to formally require the Catalan government to confirm whether it has declared independence after the deliberate confusion created over whether it has come into effect", he said in a television address on Wednesday.
"The Catalan president's answer to this questions will inform what happens over the next few days", he said. But he also said that he and Rajoy had agreed that there should be a commission to examine the possibility of changing the way the country's autonomous regions are governed through constitutional reform.
"Given that Rajoy can not accept a bilateral discussion without Puigdemont backtracking first on independence, the most likely scenario is that the prime minister activates the next steps of Article 155 (the so-called "nuclear option"), which will probably happen within the next 48 hours".
About 2.3 million Catalans, or 43 per cent of the electorate in the wealthy northeastern region, voted in the referendum.
Catalan 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 while thanking those who made them. The drive to break Catalonia away from Spain has raised concern for stability in a European Union still coming to terms with Britain's shock decision to leave the bloc.
"Morocco is confident in the ability of the Spanish government to wisely manage this situation with a view to preserving the constitutional order and to act in the supreme interest of the Spanish Nation and the European Continent", said the statement.
Crowds of thousands gathered outside the parliament building in Barcelona on Tuesday ahead of Puigdemont's speech, waving Catalan flags and banners and screaming "democracy" in the hope of witnessing history in the making.