Starbucks’ union members have voted to strike at the company’s United States stores this week unless it finalizes a contract agreement, the union said.

The strike would begin on Thursday, which is the day Starbucks plans to distribute free, reusable red cups. Red Cup Day, a Starbucks tradition since 2018, typically is one of the company’s busiest days of the year.

Starbucks Workers United, the union organizing baristas, didn’t say how many stores would be impacted. It said workers in at least 25 cities planned to strike and more locations could be added if the union doesn’t see “substantial progress” toward finalizing a contract.

Around 550 of Starbucks’ 10,000 company-operated U.S. stores currently are unionized. More stores have voted to unionize since 2021, but Starbucks closed 59 unionized stores in September as part of a larger restructuring.

Starbucks said it’s disappointed the union plans to strike instead of returning to the bargaining table.

“Any agreement needs to reflect the reality that Starbucks already offers the best job in retail, including more than $30 an hour on average in pay and benefits for hourly partners,” Starbucks spokeswoman Jaci Anderson said.

In a letter to Starbucks employees last week, Starbucks’ Chief Partner Officer Sara Kelly said the union has proposed a 65 percent pay increase immediately and a 77 percent increase over three years, with additional payments for things such as weekends or days when Starbucks runs promotions. Kelly also said some proposals would significantly alter Starbucks’ operations, such as giving workers the ability to shut down mobile ordering if a store has more than five orders in the queue.

The union said Starbucks is unfairly lumping together various economic proposals from the union to arrive at those pay raise figures.