Workers at seven Amazon facilities went on strike Thursday, an effort by the Teamsters to pressure the e-commerce company for a labor agreement during a key shopping period.

The Teamsters say the workers, who authorized strikes in the past few days, are joining the picket line after Amazon ignored a Sunday deadline the union set for contract negotiations. Amazon says it doesn’t expect an impact on its operations during what the union calls the largest strike against the company in U.S. history.

The International Brotherhood of Teamsters say they represent nearly 10,000 workers at 10 Amazon facilities, a small portion of the 1.5 million people Amazon employs in its warehouses and corporate offices.

At one warehouse, located in New York City’s Staten Island borough, thousands of workers who voted for the Amazon Labor Union in 2022 and have since affiliated with the Teamsters. At the other facilities, employees - including many delivery drivers - have unionized with them by demonstrating majority support but without holding government-administered elections.

The strikes happening Thursday are taking place at one Amazon warehouse in San Francisco, California, and six delivery stations in southern California, New York City; Atlanta, Georgia, and Skokie, Illinois, according to the union’s announcement. Amazon workers at the other facilities are “prepared to join,” the union said.

“Amazon is pushing its workers closer to the picket line by failing to show them the respect they have earned,” Teamsters General President Sean M. O’Brien said in a statement.

The Seattle-based online retailer has been seeking to re-do the election that led to the union victory at the warehouse on Staten Island, which the Teamsters now represent. In the process, the company has filed a lawsuit challenging the constitutionality of the National Labor Relations Board.