CNN  — 

President Joe Biden on Sunday night lent his support to Amazon (AMZN) workers who are pushing to unionize — and appeared to warn Amazon (AMZN) not to deter them.

In a video posted on Twitter, Biden didn’t mention the company by name, but he did reference workers in Alabama, where a milestone union election is underway at an Amazon facility in Bessemer. Eligible workers at the facility are currently voting by mail to decide whether to form Amazon’s first US-based union.

“Today and over the next few days and weeks, workers in Alabama, and all across America, are voting on whether to organize a union in their workplace,” Biden said in the video.

“There should be no intimidation, no coercion, no threats, no anti-union propaganda,” Biden continued. “No supervisor should confront employees about their union preferences. You know, every worker should have a free and fair choice to join a union. The law guarantees that choice.”

Amazon did not immediately respond to a request for comment.

Biden’s remarks reflect the high profile of the Amazon vote, which has garnered national attention and support from prominent Democrats including Senators Elizabeth Warren and Bernie Sanders as well as Stacey Abrams. A group of 50 Congresspeople sent a letter last month urging Amazon’s outgoing CEO, Jeff Bezos, to “treat your employees as the critical asset they are, not as a threat to be neutralized or a cost to be minimized.”

Biden’s decision to weigh in on the issue also exemplifies how he will try to fulfill his promise to be a very pro-union president.

Stuart Appelbaum, president of the Retail, Wholesale and Department Store Union, which is conducting the union drive for Amazon workers at the Bessemer facility, thanked Biden “for sending a clear message of support” for the workers.

“As President Biden points out, the best way for working people to protect themselves and their families is by organizing into unions. And that is why so many working women and men are fighting for a union at the Amazon facility in Bessemer, Alabama,” Appelbaum said in a statement.

The President’s video statement follows a letter cosigned by dozens of advocacy organizations last week calling on Biden to support the Bessemer plant’s workers. “During the 2020 campaign, you vowed to be ‘the most pro-union president you’ve ever seen.’ This is a once-in-a-generation opportunity to make that pledge a reality. We urge you to lend all your support to the Amazon workers in Bessemer,” read the letter. “They deserve nothing less.”

As CNN Business has previously reported, Amazon waged an aggressive anti-union campaign leading up to the vote, which began on February 8 and runs through March 29.

Workers were frequently informed of Amazon’s stance that a union is an unnecessary expense in a variety of ways. Workers saw anti-union signage on the bathroom stalls when using the toilet; they were pulled into one-on-one meetings on the warehouse floor and were also required to attend group meetings every few shifts. The company sent out numerous text messages to workers and launched an anti-union website that warns against paying dues: “Don’t buy that dinner, don’t buy those school supplies, don’t buy those gifts because you won’t have that almost $500 you paid in dues.”

In the video, Biden added that it is not up to him, and it is not up to employers, to decide whether workers should form a union for themselves.