Wage strikes and labor issues come at one of the busiest times of the year.
The Starbucks strike has expanded to 300 of its coffee shops in the United States, with more than 5,000 workers expected to walk off the job, the labor union said.
The strike for five days will end Tuesday, and comes in the middle of the Christmas holiday, one of Starbucks' busiest times of the year.
Starbucks Workers Unitedrepresenting workers at 525 stores across the country, said more than 60 US stores in 12 major cities, including New York, Los Angeles, Boston and Seattle, were closed on Monday.
Negotiations between Starbucks and the union have been marred by unresolved issues over pay, staffing and scheduling, leading to a strike that began Friday.
With a collective agreement, benefits, wages, and working conditions can be written and cannot be reduced without negotiation, according to the Workers United website.
The Christmas strike on Tuesday is expected to be the largest of its kind in the coffee sector, the union added. “This strike is an early show of strength, and we're just getting started,” Oregon baristas said in a joint statement.
Starbucks, which operates more than 10,000 company-owned stores in the US, said 98 percent of its stores remained open, while about 170 stores were closed Tuesday.
The company said on Monday that it expects “significantly lower” operating costs.
“We are ready to continue negotiations when the deal comes back to the negotiating table,” the company said.
The Seattle-based company previously said union representatives had ended negotiations.
Earlier this month, the union rejected a decision not to raise wages immediately and a guarantee of 1.5 percent wage increases in future years.
The union also said that Starbucks did not give its workers “great economic benefits”.