(NEW YORK) — Hundreds of Starbucks employees went on strike Thursday, amid the coffee chain’s busy holiday season, to protest working conditions and push company leaders to recognize workers’ unionizing efforts at stores nationwide and meet them at the bargaining table.

The protest took place on Starbucks’ Red Cup Day, as the company rolled out its annual holiday themed red cups and gave out limited-edition reusable versions of the cups to customers ordering holiday or fall beverages.

More than 1,000 members of the Starbucks Workers Union picketed outside of over 100 stores across the country for what they called the “Red Cup Rebellion.”

Union leaders sent a mass email to media and union members with details of the strike, which it described as the “biggest coordinated national action taken by union Starbucks stores in the campaign’s history.”

The email stated that the strike was a “response to Starbucks’ union-busting tactics and refusal to bargain,” and noted that striking workers would be “handing out red Starbucks Workers United union cups to customers instead.”

As customers headed in to order coffee and get their hands on the collectible holiday reusable cups, many baristas said they would walk out in protest.

“Despite being the face of the company, Starbucks partners are underpaid, forced to run perpetually understaffed stores, and don’t have consistent schedules they can rely on,” the union email stated. “Conditions like these are what lead Starbucks partners nationwide to begin their unionization efforts seeing the private jets and million-dollar bonuses the company can afford to provide their executives with. Now, Starbucks partners are demanding the right to organize a union free of intimidation and fear.”

Vermont Sen. Bernie Sanders voiced his support for the group’s efforts on Twitter Thursday morning.

“I’m proud to stand with Starbucks workers on strike today across the country. CEO Howard Schultz is illegally union busting and firing workers for organizing. Mr. Schultz, it is time to recognize the stores that unionized and negotiate with workers in good faith,” he wrote.

Michelle Eisen, a worker from the first unionized Starbucks store in the U.S. at Elmwood Ave. in Buffalo, New York, wrote in the email that workers are “organizing for a voice on the job and a true seat at the table.”

“Starbucks has left behind the very values that drew many of us to the company in the first place. You cannot be pro-LGTBQ, pro-BLM, pro-sustainability, and anti-union,” she said.

A spokesperson for the Seattle-based coffee chain told ABC News the company was aware of the scheduled union demonstrations at a small number of their U.S. stores.

“In those locations where partners choose to participate, we respect their right to engage in lawful protest activity – though our focus has been, and continues to be, on uplifting the Starbucks experience for our partners and customers,” they said. “We remain committed to all partners and will continue to work together, side-by-side, to make Starbucks a company that works for everyone.”

Additionally, the spokesperson clarified that “counter to what the union has shared, Starbucks has continued to engage Workers United representatives in a good faith effort to move the bargaining process forward.”

“As a result of our efforts, we’ve shown up to more than 50 bargaining sessions across the country and have another 60 scheduled in the coming weeks,” they said.

Starbucks Workers United, which represents over 260 locations and nearly 7,000 workers, has formed more new unions in a 12-month period than any U.S. company in the last 20 years.

In September, Starbucks said it had sent out letters to 234 stores to schedule bargaining sessions the following month. “We look forward to these negotiations and hopefully setting dates and securing locations for contract bargaining.”

However talks broke down after union members asked to allow some workers to join bargaining sessions over Zoom, with company officials walking out of those sessions only minutes after they had begun, citing federal regulations.

“The National Labor Relations Board (NLRB) prohibits any party from making recordings or transcripts of contract negotiations because such actions ‘inhibit the free and open discussion necessary for conducting successful bargaining,’ ” the company wrote in a statement on Oct. 28.

Union members also issued a statement at that time. “Workers across the country were planning on presenting a set of core non-economic proposals that workers debuted on social media over the past few weeks,” they wrote. “The Union will be filing a new NLRB charge over the Company’s latest refusal to bargain in good faith.”

The National Labor Relations Board has issued 39 official complaints against Starbucks, encompassing over 900 alleged violations of federal labor law, according to the union.

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