With the pardons the cabinet will rubber-stamp at its weekly meeting on Tuesday, Sanchez aims to ease tensions in the northeastern region and kick-start negotiations between the central government and Catalan authorities.

"Confrontation didn't serve to solve any problem," Sanchez said in speech at Barcelona's iconic opera house on Monday in an event attended by about 300 members of the Catalan civil society.

"To reach an agreement someone must make the first step," he said. "The Spanish government will make that first step now."

Nine separatist leaders were handed lengthy prison sentences for sedition and other crimes linked to a banned secession referendum and for declaring independence a few days later based on its results, even when most unionists boycotted the vote.

Opinion polls show about 60 per cent of Spaniards - as well as all opposition parties - are against freeing the nine politicians and activists who were jailed in 2019 for their role in the chaotic and at times violent events that triggered Spain's biggest political crisis in decades.

Australian Associated Press