(Reuters) -Starbucks workers have expanded their strike to four more U.S. cities, including New York, the union representing over 10,000 baristas said late on Saturday.

The five-day strike, which began on Friday and initially closed Starbucks cafes in Los Angeles, Chicago and Seattle, has added locations in New Jersey, New York, Philadelphia and St. Louis, Workers United said in a statement. It did not specify in what New Jersey city the walkout was occurring.

Starbucks said the disruptions from the strike have no significant impact on its operations because only a small handful of U.S. stores have been impacted.

"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," the coffee chain said.

The union is striking in 10 cities, also including Columbus, Ohio, Denver and Pittsburgh, during the busy holiday season that may impact the company's Christmas sales.

The group did not immediately respond to a Reuters request for comment on the number of stores on strike on Monday.

The company operates more than 11,000 stores in the United States, employing about 200,000 workers.

Talks between Starbucks and the union hit an impasse with unresolved issues over wages, staffing and schedules, leading to the strike.

Workers United warned on Friday that the strike could reach "hundreds of stores" by Tuesday, Christmas Eve.

Starbucks began negotiations with the union in April. It said this month it had conducted more than eight bargaining sessions, during which 30 agreements had been reached.