Unionized workers at a Maryland Apple store voted on Saturday to authorize a strike, which would mark the first such labour action against the retailer in the United States if it goes forward.

Employees at the Apple store in the town of Towson, near Baltimore, voted to unionise in 2022 -- another first for the iPhone maker's US stores.

But a contract has yet to be agreed upon.

"Following over a year of negotiations with Apple management that yielded unsatisfactory outcomes," union members are "signaling their collective demand for meaningful change," a union statement said.

"The issues at the forefront of this action include concerns over work-life balance, unpredictable scheduling practices disrupting personal lives, and wages failing to align with the area's cost of living."

The Towson store has about 100 employees. A majority of them were required to vote for the result to be valid.

The next negotiation meeting is scheduled for May 21, though a strike could come before that.

Meanwhile, employees at another of the California-based company's stores, in New Jersey, voted down a unionisation effort over the weekend.

In a statement to CNN, Apple said it would "engage with the union representing our team in Towson respectfully and in good faith."

The National Labor Relations Board, the federal labour regulator, has received numerous complaints against Apple, accusing it of trying to discourage staff from unionising.

US tech companies in general are seen as hostile toward unionisation efforts -- particularly Amazon.

In September, nearly a quarter of Apple store employees in France went on strike the day the iPhone 15 launched, demanding a pay raise at least equal to inflation. (AFP)