Spanish prosecutors want to charge Puigdemont, holed up in Belgium, with rebellion, sedition and misuse of public funds.
The time has come for all democrats to unite.
Mr Puigdemont, 54, told Belgium television that he wanted to appear "before the true Justice (of Belgium), not before the Spanish".
Catalonia's ousted leader says he's ready to cooperate with Belgian authorities after Spain issued a European warrant for his arrest, though he isn't giving any clues about his whereabouts.
Former Catalan President Carles Puigdemont and several members of his separatist government fled north to Brussels after Spanish authorities removed the region's top officials from office a week ago.
"The fury with which the Spanish government has attacked a handsome European nation is outrageous and is threatening us all", Mr Puigdemont said, adding that Catalonia's independence is "no longer an internal affair" of Spain. "For Catalonia, for the freedom of political prisoners and the Republic", he wrote, endorsing calls for pro-secession political parties to unite in a coalition for the forthcoming poll. Puigdemont's lawer said he would appeal any negative decision.
Madrid last month dissolved Catalonia's parliament after regional lawmakers voted to declare independence from Spain off the back of a banned referendum on the issue. Puigdemont has left the door open to running.
In a tweet, he referred to an online petition calling for the creation of a combined independent candidate list, which by today afternoon had received over 50,000 signatures.
But the longer Mr Puigdemont can delay his arrest and extradition, the greater chance he has of being a factor in the December 21 election that Spanish authorities have called as part of their temporary takeover of running the rebellious region.
But there have been growing tensions between the two allies over strategy and it is not clear if they will stand together again.
"Elections here can only happen here if we say they do", Rovira said. The other four people named in warrants are Toni Comin, Clara Ponsati, Lluis Puig and Meritxell Serret.
Spain's state prosecutor had asked the judge to issue such a warrant earlier in the day.