A group of employees at an Apple Inc store in Maryland has started a drive to form a union.
Organizers of the move said they had signatures from more than 65% of employees who are likely to be eligible.
The union intends to file paperwork with the National Labor Relations Board in the coming days.
Earlier, in April, workers at an Apple store in Atlanta filed a petition to hold a union election.
There have also been a wave of labour activity at other major firms as Amazon.com Inc workers voted against unionizing a second warehouse in New York City.