Counting of votes cast by Amazon employees at an Alabama warehouse began Tuesday to determine whether it would become the first union shop at the e-commerce colossus.
Legal wrangling over whether some ballots should be disqualified was expected to slow the process for days, with Amazon anticipated to seek to prevent unions from getting a foothold in its massive operations.
"We encouraged all of our employees to vote, and their voices will be heard in the days ahead," an Amazon spokesperson told AFP.
"Our employees know the truth -- starting wages of $15 or more, health care from day one, and a safe and inclusive workplace."
Tally of the ballots, which have been cast by mail since February 8, will take place behind closed doors, overseen by the National Labor Relations Board. Eligibility of votes can be challenged for reasons such as signing in the wrong place or misstating a job role.
The Retail, Wholesale and Department Store Union would represent the 5,800 employees at the Bessemer sorting and packaging site if a majority votes in favor.
Coming at a time when US President Joe Biden has promised to be the country's "most pro-union president," the Bessemer effort could open the floodgates to organizing drives at other Amazon sites, as well as at other firms.
Unions and political leaders have argued that Amazon employees face constant pressure and monitoring, with little job protection, highlighting the need for collective bargaining.
Amazon has argued that most of its workers don't want or need a union and that it already provides more than most other employers, with a minimum $15 hourly wage and other benefits.