The demonstrators want to replace Chile’s dictatorship-era constitution that concentrates power in the presidency with a new charter. They say it should enable popular referenda and enshrine free education as a right for all citizens. Striking unions also want pension reform and more investments in health and education.

President Sebastian Pinera’s spokesman Andres Chadwick has dismissed the demands as “utopian.”

Vast numbers of Chileans are now expected to stay off the job Wednesday and Thursday, costing millions in lost production.