BURBANK, Calif. — Starbucks workers Monday are set to expand a nationwide strike against the coffee giant, three days after a walkout closed one of the company's Burbank locations at Alameda Avenue and Shelton Street.

The strike, led by Starbucks Workers United, began Friday morning in key markets, including Los Angeles, Chicago and Seattle. Walkouts are expected to expand daily and impact hundreds of stores nationwide by Christmas Eve, the union said.

On Sunday, union baristas in New Jersey, New York, Philadelphia and St. Louis joined others who have already begun strikes in Los Angeles, Chicago, Columbus, Denver, Pittsburgh and Seattle. Workers shut down dozens of stores Saturday, and their walkouts are expected to keep growing through the final days of holiday shopping before Christmas.

"The few disruptions we have experienced this week have had no significant impact to our store operations. Only a small handful of our US stores have been impacted," a Starbucks representative told City News Service Saturday.

"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 added.

The union is accusing Starbucks of failing to honor earlier commitments to improve collective bargaining and resolve legal disputes. Starbucks Workers United says the company proposed an economic package with no new wage increases for union baristas and a guarantee of only 1.5% in future years.

"Nobody wants to strike. It's a last resort, but Starbucks has broken its promise to thousands of baristas and left us with no choice," Fatemeh Alhadjaboodi, a bargaining delegate, said in a statement. "In a year when Starbucks invested so many millions in top executive talent, it has failed to present the baristas who make its company run with a viable economic proposal."

Starbucks maintains it is committed to reaching an agreement and is willing to return to the bargaining table, claiming the union was the one to cut off negotiations.

"It is disappointing they didn't return to the table given the progress we've made to date. Since April we've held more than nine bargaining sessions over 20 days," according to a statement from the company. "We've reached over thirty (30) meaningful agreements on hundreds of topics Workers United delegates told us were important to them, including many economic issues."

The company said it offers an average wage of more than $18 an hour and provides what it calls best-in-class benefits, including health care, free college tuition, paid family leave and stock grants.

Meanwhile, baristas at the Starbucks on Sunset Boulevard and La Brea Avenue filed a petition Friday with the National Labor Relations Board for a union election, seeking to join more than 520 Starbucks locations across the country where baristas are unionized.