SILAO, Mexico, Aug 17 (Reuters) – General Motors (GM.N) employee Mari says that for the past decade, she has felt powerless to demand higher pay at the plant in central Mexico that cranks out hundreds of thousands of profitable pickup trucks annually.

But on Tuesday and Wednesday, the plant’s nearly 6,500 unionized workers are to vote on what Mari and many coworkers see as a historic opportunity to oust their union, which they say protects the company’s interests over their own.

If workers reject the Miguel Trujillo Lopez union, it would open the door for them to bring in new representation.

The vote marks the first major test of labor rules under the United States-Mexico-Canada Agreement (USMCA), a regional trade deal that replaced NAFTA and aims to foster stronger unions and boost wages in Mexico, in part to reduce incentives for U.S. companies to move jobs south of the border.