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

Unionized Starbucks workers in Boston on Monday joined a nationwide strike to protest lack of progress in contract negotiations with the company.

Starbucks workers have expanded their strike to more cities and closed 59 stores across the U.S. as of Monday, the union said amid stalled negotiations.

The strikes by baristas and other workers were scheduled to take place in Los Angeles, Chicago and Seattle and could spread to hundreds of stores across the country by Christmas Eve. The planned walkouts would come a day after the Teamsters union announced strikes at seven Amazon delivery hubs.

Starbucks' union says workers are walking off the job at some 300 — out of over 10,000 — stores across the U.S. as contract negotiations falter. The company urges it to return to the bargaining table.

Starbucks Workers United told USA TODAY that employees in Boston, Dallas-Fort Worth, and Portland, Oregon also joined picket lines.

The union representing Starbucks workers said its five-day strike will conclude on Tuesday with the strike spreading to more than300 stores, adding more establishments in metro areas.

The chain's hours vary by location, meaning some will be open while others may be closed. The company recommends customers check with their closest location to confirm their specific holiday hours. Customers can also use the store locator function on the Starbucks app or website for information regarding their local Starbucks shop.

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