Currently, unfair labor practice strikes are limited to Safeway/Albertsons locations in just four cities: stores in Estes Park, Fountain and Pueblo, and a distribution center in Denver.

About 45,000 grocery workers have authorized a strike at Ralphs, Albertsons, Vons and Pavilions stores in Southern California to protest unfair labor practices.

With the clock winding down toward Saturday night's deadline for new contract negotiations, a Colorado union has announced locations where grocery employees are set to walk off the job on Sunday in protest.