Catalan leader Quim Torra renewed calls for Madrid to accept a referendum on independence in an interview published on Sunday, two days before separatists take to the streets in the first of a series of major protests.
Following an easing of tensions between the secessionist Catalan government and Madrid in recent months, Torra last week rejected anything other than a full independence referendum.
"If the Spanish government doesn't see this as a negotiable position then we will press ahead because we have a democratic mandate," Torra said in an interview published on Sunday in Catalan newspaper El Periodico.
Hundreds of thousands of Catalan secessionists are expected to take to the streets of Barcelona on September 11 to mark a regional holiday which in recent years has proved a catalyst for separatist sentiment.
Torra also repeated demands for charges to be dropped against nine separatist leaders accused of crimes including rebellion for their role in last year's banned referendum and a subsequent failed declaration of independence.
The trial could begin as early as October, further raising tensions as Prime Minister Pedro Sanchez seeks to reach a compromise with the Catalan government.