“The time has come for all democrats to unite. For Catalonia, for the release of political prisoners and for the republic,” Puidgemont said on Twitter.
A Spanish judge on Friday issued an EU arrest warrant for Puigdemont, who is holed up in Belgium and failed to turn up for questioning over his role in the push for Catalonia to break away from Spain.
On Thursday, the judge ordered Puigdemont's deputy and seven other deposed regional ministers detained pending a possible trial, triggering angry demonstrations.
Puigdemont had said on Friday he was ready to run as a candidate in the December 21 vote, which was called by Spain after it imposed direct rule on Catalonia and sacked the regional authorities in the wake of the parliament's declaration of an independent republic.
In his tweet, Puigdemont referred to an online petition calling for the creation of a combined independent candidate list, which by Saturday had received more than 34,000 signatures.
Spanish prosecutors want to charge Puigdemont and another four ex-ministers who are in Belgium with rebellion, sedition and misuse of public funds.
Puigdemont, who continues to describe himself as the “legitimate” president of Catalonia, is a member of the PDeCAT party which has been in power in the wealthy northeastern region for much of Spain's modern democratic era.
Separatist parties have 72 seats in the 135-seat Catalan parliament but the PDeCAT is seen running fourth or fifth in the December vote according to opinion polls.