A five-day strike by Starbucks baristas had closed 59 stores as of Monday afternoon, according to the union organizing the workers.

The strike, which began Friday in Los Angeles, Chicago and Starbucks' hometown of Seattle, spread Monday to stores in Boston, Dallas and Portland, Ore. Workers in New York, Denver, Pittsburgh and other cities had also joined the strike over the weekend.

Workers are protesting a lack of progress in contract negotiation with the company. Starbucks Workers United, which began the unionization effort in 2021, said Starbucks has failed to honor a commitment made in February to reach a labor agreement this year.

The union also wants the company to resolve outstanding legal issues, including hundreds of unfair labor practice charges that workers have filed with the National Labor Relations Board. Since 2021, baristas at 535 company-owned U.S. Starbucks stores have voted to join the union.

The strike comes at one of the busiest times of the year for Starbucks. But the company said Monday it has had "no significant impact" to its store operations. Starbucks has around 10,000 company-operated stores in the U.S.

"We respect our partners' right to engage in lawful strike activity, and we appreciate the thousands of partners across the country who are continuing to support each other and deliver the Starbucks experience for our customers," the company said Monday in a statement.

The two side have been bargaining since the spring but appear to have reached an impasse over economic issues. Starbucks said it has committed to an annual pay increase of 1.5% or more for unionized workers. If the company gave a lower increase to non-union workers in any given year, it still would give union workers a 1.5% increase.

Starbucks said its U.S. baristas make an average of $18 per hour. With benefits -- including health care, free college tuition and paid family leave -- Starbucks' pay package is worth an average of $30 per hour for baristas who work at least 20 hours per week, the company said.

Workers say they deserve more, and note that Starbucks' new Chairman and CEO Brian Niccol, who started in September, could make more than $100 million in his first year on the job.