The opposition of Amazon.com Inc. to a historic union election at a corporate warehouse in New York City warrants a trial that may invalidate the vote, an officer from the United States National Labor Relations Board (NLRB) stated.

The online marketplace argues that the NLRB's Brooklyn office appeared to back the union campaign and that labor organizers coerced workers into voting in their favor, allegations that the union denies.

Amazon last month obtained the case's relocation to the NLRB's Phoenix-based region, alleging the Brooklyn office's actions.

Based on a filing on Friday, the head of that office, Cornele Overstreet, said the evidence supporting Amazon's allegations may be grounds for invalidating the election.

Roughly 55% of workers at Amazon's JFK8 facility in the Staten Island district voted to join the Amazon Labor Union (ALU), which has fought for improved pay and job security. About 58% of people participated.

The election was the first time in Amazon's roughly 28-year history that U.S. employees voted to unionize, a triumph for organized labor, which has pushed for better workers' rights at the nation's second-largest private company for years.

Overstreet did not say which of Amazon's 25 complaints could be used to overturn the election results. Beginning May 23, he said, the parties can give testimony, following which an NLRB hearing officer will consider whether the decision should be upheld. 

The bar for getting a hearing is extremely low, according to Eric Milner, a counsel with the ALU, and no authority has yet evaluated Amazon's supposed proof.

"While the ALU is upset that Amazon is delaying its negotiating commitments, we remain convinced that all of Amazon's concerns will be overturned in the end," he said. 

"We need our workers to have their voices be heard, and in this situation, that didn't happen - less than a third of the workforce at the facility voted for the union," said Amazon spokesperson Kelly Nantel.

Analysts claim the tenacious union is hindered by a lack of organizers, but that may not be a problem because the ALU's reputation has been supported by its surprising victory last month.

Top union leaders and prominent progressive Public officials have also endorsed it. Last Monday, at a protest outside the warehouse the day before voting began, U.S. Senator Bernie Sanders and Representative Alexandria Ocasio-Cortez spoke out in favor of the union activists.