Starbucks workers union are on strike in three U.S. cities on Friday. The strike, reps say, could soon spread across the nation.

Starbucks baristas went on strike at several stores in Chicago, Seattle and Los Angeles on Friday, with their union warning the walkouts could spread to hundreds of cafes by Christmas Eve if the coffee giant does not meet workers’ demands at the bargaining table.

Unionized Starbucks workers are staging a days-long protest during the company's peak holiday season over a failure to come to a contract agreement.