Starbucks union strikes on Friday in LA, Chicago and Seattle

The labor union, which represents more than 10,000 Starbucks baristas, said union members will go on strike in Los Angeles, Chicago and Seattle on Friday morning.

Workers United, which has a bargaining delegation representing workers at 525 Starbucks stores in the U.S., said walkouts are expected to spread each day and reach hundreds of stores from coast to coast by Christmas Eve unless Starbucks ( SBUX ) and the union reach an agreement.

The union and Starbucks created a “framework” in February to guide organizing and collective bargaining. Negotiations between the company and Workers United began in April, based on the framework, which could also help resolve several pending legal disputes.

“Since the February commitment, the company has repeatedly promised publicly that it intended to conclude contracts by the end of the year, but it has yet to present workers with a serious financial proposal,” the union said in a declaration late on Thursday.

Starbucks said the union “prematurely” ended a bargaining session this week.

“It is disappointing that they did not return to the table given the progress we have made to date,” the company said in a statement. “We are ready to continue negotiations to reach an agreement. We need the union to return to the table.”

The union has called on Starbucks to increase wages and staff at its stores, as well as implement better schedules.

Starbucks has faced a difficult year: Sales have fallen for three straight quarters, the longest decline in years. Some customers have stopped going to Starbucks because of high drink prices and long wait times, and hundreds of its stores have voted to unionize in protest over wages, benefits and working conditions.

In August, the struggling coffee chain had tapped Chipotle CEO and corporate fix-it man Brian Niccol to be its new chairman and CEO, effective Sept. 9.

In just his second day on the job, Niccol said in a letter to employees and customers that he wants to bring Starbucks back to its roots as a “community coffeehouse” with comfortable seating, design and a clear distinction between “to-go” and ” for-here” service.

CNN’s Jordan Valinsky contributed reporting.