San Francisco, March 1 (IANS): US President Joe Biden has offered his support to unionisation efforts of workers, as employees of Amazon in an Alabama warehouse vote on whether to unionise.

While Biden did not mention Amazon, the reference was clear when he mentioned "workers in Alabama" in a video produced by the White House. He defended the workers' right to decide whether to form a union without intimidation by employers.

"Workers in Alabama -- and all across America - are voting on whether to organize a union in their workplace. It's a vitally important choice -- one that should be made without intimidation or threats by employers," the US President said in tweet introducing the video late on Sunday.

Amazon workers at the Bessemer, Alabama, warehouse started voting by mail starting February 8.

Nearly 6,000 workers are to mail back their ballots by March 29 on whether to join the Retail, Wholesale and Department Store Union (RWDSU).

"Unions lift up workers, both union and non-union, but especially Black and Brown workers," Biden said in the video.

"There should be no intimidation, no coercion, no threats, no anti-union propaganda. No supervisor should confront employees about their union preferences."

He said that unions put power in the hands of workers and that they level the playing field.

"They give you a strong voice for your health, your safety, higher wages, protection from racial discrimination and sexual harassment," Biden said.

Amazon's bid to postpone a union vote at a warehouse in Alabama was earlier rejected by the country's National Labor Relations Board (NLRB).

Amazon appealed in January to prevent a mail-in vote by the warehouse workers on whether to join the Retail, Wholesale and Department Store Union.

The NLRB, in its ruling, said that Amazon's appeal raised "no substantial issues warranting review," CNBC reported.

The voting is being closely watched as it is the first major unionisation effort within Amazon since 2014 when similar efforts by repair technicians at a warehouse in Delaware failed as they could not get enough votes required for joining a union.

In what appears to be a bid to discourage the union drive, Amazon set up a website reminding workers that joining a union will cost them money in the form of membership dues.

"Why pay almost $500 in dues? We've got you covered* with high wages, health care, vision, and dental benefits, as well as a safety committee and an appeals process. There's so much MORE you can do for your career and your family without paying dues," said the website doitwithoutdues.com in its appeal to Bessemer employees.