The company also highlighted that it offers average pay of more than $18 (£14.40) an hour, as well as “best-in-class benefits”.
“Combined, they average $30 an hour for baristas who work at least 20 hours a week,” it said.
Workers United says it represents workers at more than 500 stores in 45 US states.
“This is a last resort, but Starbucks has broken its promise to thousands of baristas and left us with no choice,” Fatemeh Alhajaboudi, a Starbucks barista in Texas, said in a statement sent to the BBC by the union.
Workers United has highlighted what it sees as an unfair pay disparity between its members and senior executives at Starbucks, including Executive Director Brian Nicol.
His annual salary is $1.6 million. He also could receive a $7.2 million performance bonus and up to $23 million a year in Starbucks stock.
Starbucks previously defended the plan, saying Mr. Nichol was “one of the most effective leaders in our industry” and that his compensation was “directly tied to the company’s performance and the overall success of all our stakeholders.”
Mr. Nicol joined the company in September after his predecessor Laxman Narasimhan stepped down after less than two years.
Sales of the world’s largest coffee chain are falling as it battled a backlash against price hikes and boycotts sparked by the war between Israel and Gaza.
The Starbucks strike is happening as one of the most powerful unions in the US is organizing a protest against Amazonin a bid to put pressure on the tech giant, which is rapidly churning out packages in the run-up to Christmas.
The Teamsters union said Amazon delivery drivers at seven U.S. sites walked off Thursday after the company refused to negotiate a labor contract with the union.
