The International Brotherhood of Teamsters may take on Amazon at a time when the company is aggressively combating unionization efforts.

The Teamsters are the most well-known union in the US, with a long and storied history. The group also boasts some 1.4 million delivery drivers, putting it on a collision course with Amazon.

Amazon has drawn significant criticism in recent years for its treatment of its workers, including delivery drivers. As recently as February, the company settled with the FTC for some $62 million dollars over its practice of illegally withholding tips from its drivers.

The company has aggressively fought unionization efforts by its employees, however, successfully defeating an effort by warehouse workers in Alabama. The Teamsters have already come out swinging against the e-commerce giant, urging the House Judiciary to pass antitrust legislation that would target Amazon.

On Thursday, the union will vote on whether to make unionizing Amazon drivers its top priority, according to The Seattle Times.

“There is no clearer example of how America is failing the working class than Amazon,” says the resolution that will be voted on.