Employees at many Apple stores in the United States are working to unionize, the Washington Post reported on Friday, citing people familiar with the efforts.

The move comes against the backdrop of unionization efforts gaining momentum at large U.S. corporations, including Amazon and Starbucks.

The report said employee groups at least two Apple retail stores are backed by major national unions and are preparing to file paperwork with the National Labor Relations Board (NLRB) in the near future.

At least six more locations are at less advanced stages in the unionization process, the report said, adding that Apple employs more than 65,000 retail workers.

Apple and the NLRB did not immediately respond to Reuters requests for comment.

Apple has 270 stores in the country and made 36% of its total $365.82 billion net sales in fiscal 2021 through its retail stores and website, according to a regulatory filing.

Its boss Tim Cook's pay last year was 1,447 times that of the average employee at the tech giant, fueled by stock awards that helped him earn a total of nearly $100 million.

The company had decided to temporarily shutter several outlets across the United States during the peak of the COVID-19 pandemic.

Last year, it planned to give store workers one-time bonus of as much as $1,000, Bloomberg News had reported in September, amid tight labor market conditions and unrest among employees.