Starbucks Workers United initiated an open-ended strike on Thursday in at least 40 cities, coinciding with Red Cup Day, one of the chain’s busiest sales periods, News.Az reports, citing CNBC.

A strike at Starbucks has expanded to over 300 of the coffee chain's stores in the United States, with more than 5,000 workers expected to walk off the job, according to the workers' union, News.az reports citing Al Jazeera.

A strike at Starbucks U.S. stores is set to expand to over 300 locations on Tuesday, with more than 5,000 workers expected to join the walkout, according to the workers' union.