U.S. President Joe Biden said he was "proud" of Apple Inc. workers in Maryland who voted on Saturday to join a union, becoming the first retail employees of the tech giant to unionize in the United States.

"I am proud of them," Biden told reporters on Monday. "Workers have a right to determine under what condition they are going to work or not work."

More than 100 workers in Towson near Baltimore "overwhelmingly voted to join the International Association of Machinists and Aerospace Workers," the union said on its website on Saturday. Apple declined to comment after the announcement.

Unionization efforts are gaining momentum at some large U.S. corporations, including Amazon.com Inc and Starbucks Corp.

"Everybody is better off, including the final product is always better off (because of unions)," Biden said on Monday when asked about the Apple workers who voted to join a union.

Widely considered the most pro-union president in decades, Biden has reversed rules of former President Donald Trump that critics said weakened worker protections.

Apple workers in Atlanta who were seeking to unionize withdrew their request last month, claiming intimidation.

Some current and former Apple workers last year began criticizing the company's working conditions online, using the hashtag #AppleToo.