(This Dec. 21 story has been corrected to remove the word 'contract', in paragraph 14)

By Savyata Mishra, Gursimran Mehar and Renee Hickman

(Reuters) - Some members of the Starbucks workers' union that represents more than 10,000 baristas walked off their jobs in multiple U.S. cities on Friday, citing unresolved issues over wages, staffing and schedules.

The five-day strike, which began on Friday and closed Starbucks cafes in Los Angeles, Chicago and Seattle, will expand to Columbus, Denver, and Pittsburgh through Saturday, the union said in a statement.

This is the latest in a series of labor actions that have picked up pace across service industries following a period when workers at manufacturers in the automotive, aerospace and rail industries won substantial concessions from employers.

At Starbucks, the Workers United union, which represents employees at 525 stores across the U.S., said late on Thursday that walkouts would escalate daily, and could reach "hundreds of stores" nationwide by Christmas Eve.

"It's estimated that 10 stores out of 10,000 company-operated stores did not open today," Starbucks said, adding that there was no significant impact to store operations on Friday.

Around 20 people joined a picket line at a Starbucks location on Chicago's north side, buffeted by snow and wind, but cheering in response to the honking horns of passing cars.

A few confused customers tried to walk into the closed store before strikers began chanting, but union member Shep Searl said the reaction had been mostly positive.

Searl said 100% of the unionized workers at the Starbucks location in Chicago's Edgewater neighborhood were participating in the strike, and according to the workers, they have been subject to numerous unfair labor practices including write-ups, "captive-audience" meetings and firings.

The union member said they made about $21 an hour and added, "that would have been a great wage in 2013."

It is an inadequate wage, the baristas said, given inflation and the high cost of living in a large city, especially since they rarely get 40-hour work weeks.

WORKERS SNUB OFFER

Negotiations between the company and Workers United began in April, based on an established framework agreed upon in February, which could also help resolve numerous pending legal disputes.

The company said on Thursday it has held more than nine bargaining sessions with the union since April, and reached more than 30 agreements on "hundreds of topics," including economic issues.

The Seattle-headquartered firm said it is ready to continue negotiations, claiming the union delegates prematurely ended the bargaining session this week.

The union, however, said in a Facebook post on Friday that Starbucks had yet to present a serious economic proposal with less than two weeks remaining until a year-end deadline.

The workers' group also snubbed an offer of no immediate wage hike and a guarantee of a 1.5% increase in future years.

"Workers United proposals call for an immediate increase in the minimum wage of hourly partners by 64%, and by 77% over the life of a three-year contract. This is not sustainable," Starbucks said on Friday.

In response to Starbucks' statement on the proposals, Michelle Eisen, a Starbucks barista and bargaining delegate, said, "Starbucks' characterization of our proposals is misleading and they know it. We are ready to finalize a framework that includes new investments in baristas in the first year of contracts."

Separately, the baristas' union said on Friday that it filed a new labor practice charge against the coffee house, alleging Starbucks "refused to bargain and engaged in bad faith bargaining" over economic issues.

Hundreds of complaints have been filed with the National Labor Relations Board (NLRB), accusing Starbucks of unlawful labor practices such as firing union supporters and closing stores during labor campaigns. Starbucks has denied wrongdoing and said it respects the right of workers to choose whether to unionize.

WORKING ON A TURNAROUND

Last month, the NLRB said that Starbucks broke the law by telling workers at its flagship Seattle cafe that they would lose benefits if they joined a union.

"It's (the strike) taking place during one of the busiest times of the year for Starbucks, which could magnify its impact while bringing unwanted public scrutiny into the company's labor practices," Emarketer analyst Rachel Wolff said.

The coffee chain is working on a turnaround under its newly appointed top boss, Brian Niccol, who aims to restore "coffee house culture" by overhauling cafes and simplifying its menu among other measures.

"Given how much Starbucks is already struggling to win over customers, it can ill afford any negative publicity - or impact to sales - that the strike could bring," Wolff said.

The Starbucks workers' strike comes in the same week as Amazon.com workers at seven U.S. facilities walking off the job on Thursday, during the holiday shopping rush.

There were 33 work stoppages in 2023, the most since 2000, though far lower than in past decades, data from the U.S. Bureau of Labor Statistics showed.