Lawyers for the Catalan parliament had also warned the session scheduled for Monday would be illegal because it was to include debate of the referendum result. A Constitutional Court ruling is now in effect, forbidding any referendum from taking place.
The global credit rating agency Standard & Poors said it may downgrade the sovereign debt rating of Catalonia in the next three months as tensions with Madrid escalate over the region's push for independence.
Two million Catalans voted in favour of the region breaking away from Spain and forming an independent republic in Sunday's referendum of independence, which saw a turnout of about 40 per cent.
Catalonia's regional parliament called the meeting on Monday to evaluate the results of the referendum.
Spain's highest court had ruled the vote illegal under the Spanish constitution.
The vote was not carried out according to regular electoral standards but Puigdemont said it had lent legitimacy to the independence drive.
"The group within the Catalan government that is calling the shots is the CUP, an extremely radical group with a lot of anarchist links and they are the ones setting the agenda", Spanish Economy Minister Luis de Guindos said in a Bloomberg Television interview Thursday.
But the independence movement is pressing ahead - first with today's general strike, the largest in the region's history, and shortly, many anticipate, with a declaration of sovereignty by the Catalan parliament.
The Catalan president also accused King Felipe of Spain of acting as a mouthpiece for the Spanish government after the monarch accused Catalan authorities of attempting to break "the unity of Spain".
It is considered Spain's worst political crisis since an attempted military coup in 1981.
The moderates are trying to find a way to avoid the nuclear option of declaring independence without triggering unrest on the streets from supporters who might feel let down.
But the government statement late Wednesday said there could be no mediation unless Puigdemont backs down.
Seibert told reporters in Berlin on Wednesday that "it's the role of every government to uphold the democratic order", noting that Spain's constitutional court had previously declared the referendum to be in breach of the country's constitution. Madrid says the constitution prohibits secession and can only be changed if all Spaniards, not just Catalans, agree.
During the vote, clashes broke out between police and activists, injured hundreds of people. Thousands of pro-independence Catalonians also went on strike in Barcelona, the region's capital, to protest police violence earlier this week.