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.

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.

Union members of the United Food and Commercial Workers (UFCW) in Southern California and the Pacific Northwest have voted this week to authorize a worker strike against Kroger and Albertsons stores, Supermarket News reported.

Workers at Albertsons, Pavilions, Ralphs and Vons grocery stores will begin preparations on Thursday for a possible strike.

The union will take strike authorization votes this week after filing unfair labor practice charges against the companies last week.