The Starbucks baristas strike is spreading to more cities — and the union organizing the workers warned the walkout would affect hundreds of stores on Christmas Eve, the last day of the five-day walkout.

A strike at Starbucks will expand to over 300 U.S. stores on Tuesday, with more than 5,000 workers expected to walk off the job before the five-day work stoppage ends later on Christmas Eve, the workers' union said.