The retail workers’ union played a leading role in resisting the deal that would have brought a second Amazon headquarters to Queens in exchange for nearly $3 billion in public subsidies. The union said it was opposed to the project unless Amazon established a “fair process” for allowing warehouse workers in the city to unionize, although it said it was willing to negotiate what that meant.

At a meeting with labor leaders and Gov. Andrew M. Cuomo last month, Amazon officials agreed to continue discussing the matter, but the company abandoned the Queens project the next day.

There are no unionized Amazon warehouse employees in the United States. Last year, some workers at a warehouse in Minnesota became the first in the United States known to have negotiated with management. The employees, many of them originally from Somalia and elsewhere in East Africa, were upset about strict productivity targets that some said made it hard for Muslim workers to pray at work. Amazon has said it saw this not as a negotiation but as an exercise in community engagement.

“Amazon already offers what unions are requesting for employees,” said Ashley Robinson, an Amazon spokeswoman. “We encourage anyone to compare our overall pay, benefits, and workplace environment to other retailers and major employers.”

The union’s action on Mr. Long’s behalf is its first for a worker at the Staten Island warehouse. The union has also been involved in efforts to organize workers at Whole Foods Market, which Amazon owns.