Starbucks workers at 65 unionised US stores have gone on strike in their latest bid to pressure the coffee chain for better pay and staffing after negotiations stalled.

The union, Starbucks Workers United, is also pushing the company to resolve hundreds of unfair labour practice charges.

Talks for a contract agreement broke down in the spring, and the two sides remain at odds over key economic issues.

Starbucks said the strike on Thursday will affect fewer than 1% of its thousands of shops, adding service will continue as usual at the “vast majority” of stores.

The union, which launched four years ago, said it had won elections at more than 600 stores – roughly 5% of the chain’s company-owned US locations.

More than 1,000 union baristas in over 40 cities are participating in the unfair labour practice strike, the union said. The action was timed to coincide with Starbucks’ Red Cup Day, a major holiday sales event.

The strike could expand to more locations if the two sides fail to reach an agreement, the union said.

“We’re risking a lot,” Dachi Spoltore, a striking barista from Pittsburgh, said on a call with reporters on Thursday. “Jobs, our livelihoods, our economic security – this might be a game to Starbucks, but this isn’t a game for us.”

“We’ll be calling on all Starbucks customers who care about this company treating us fairly to pledge: no contract and no coffee.”

The walkout is limited to a fraction of Starbucks’ US locations, but it could invite unwanted scrutiny at a delicate time for the company.

The brand has faced consumer boycotts, a wave of new competitors and a customer backlash over high prices, as well as turmoil in its leadership ranks.

The arrival last year of new chief executive Brian Niccol, who led successful turnarounds at Chipotle and Taco Bell, raised hopes he could do the same for Starbucks.

Mr Niccol quickly embarked on changes, part of what he called his “Back to Starbucks” strategy. His new policies have included banning non-customers from bathrooms, enforcing a stricter dress code for staff and re-introducing comfy seating that he said would help restore the chain’s appeal.

At the same time, Starbucks has outlined plans to invest more than $500m to improve coffeehouse staffing and training.

Last month, Starbucks reported 1% growth in sales at global stores open at least one year – its first quarterly increase in almost two years. But in the US, sales were flat.

“We have more work to do, but we’re building momentum,” Mr Niccol said on a recent call with analysts.

Baristas and their union say many of the new turnaround policies, like writing on cups and offering ceramic mugs, have only added to their workload, without an adequate increase in staffing.

Rami Saied, a union barista who has worked at Starbucks for two years, joined a picket line in front of her coffee shop in Brooklyn, New York, on Thursday morning. As customers approached the store, she and her colleagues asked them to support the workers by buying their coffee elsewhere.

A fair contract, she said, would mean Starbucks negotiating over wages, scheduling and staffing.

“To me, the staffing really matters,” said Ms Saied, 27. She said she has worked hours-long shifts with just one other employee, resulting in 30-minute delays for drink orders.

“You’re just really working back-breaking work. It just leaves you without any dignity,” she said.

Kaari Harsila, 21, walked off her job as a shift supervisor at the Brooklyn store. Four years into her time at Starbucks, she said she has grown frustrated that she is unable to secure the hours she needs.

New policies, like refusing to give water and bathroom access to non-paying customers, have at times fuelled hostility in the workplace, she added.

“We just want to be able to make a liveable wage, and to be treated like people,” Ms Harsila said.

Starbucks Workers United leaders say relations improved last year, but that contract discussions stalled when Mr Niccol – who was in charge of Chipotle when it faced complaints of labour rights violations – took the helm of the company last September.

Even after the two sides agreed to bring in a mediator in January, they remained at odds over pay, staffing and hundreds of unresolved charges of unfair labour practices.

A union spokesperson said Starbucks has offered no pay raises in the first year of a contract, then 2% in the years following, which he said fails to account for inflation and the cost of healthcare. Baristas overwhelmingly voted down the contract offer in April.

The company, on the other hand, blames the union for stalled talks. The union’s demands for pay increases would “significantly affect store operations and customer experience”, Sara Kelly, the company’s chief partner officer, said in a statement last week.

“When they’re ready to come back, we’re ready to talk,” Jaci Anderson, a spokesperson for Starbucks, said in a statement.

“Any agreement needs to reflect the reality that Starbucks already offers the best job in retail,” she added, pointing to low staff turnover rates, and pay and benefits, that the company says add up to an average hourly wage of $30.