In what the United Auto Workers calls a “slap in the face,” General Motors has announced that it will build its fifth plant to manufacture electric vehicles in Ramos Arizpe, Coahuila, Mexico, where it will spend $1 billion to upgrade and expand an existing facility, the Detroit Free Press reports.

GM has four other plants in North America building electric vehicles, three in the US and one in Canada:  Spring Hill, Tennessee; Factory ZERO in Detroit and Hamtramck, Orion Assembly in Orion Township, Michigan, and CAMI in Ingersoll, Ontario, Canada.

“We are really proud about contributing to GM’s vision of a future with zero crashes, zero emissions and zero congestion, by the production of electric vehicles,” said Francisco Garza, GM Mexico president and managing director, in a statement. “We are confident that future economic conditions will enable this investment to eventually grow the complex workforce in some operations from two to three shifts.”

The UAW, however, saw the investment in Mexico as a betrayal of the company’s pledge to increase the US workforce.

“At a time when General Motors is asking for a significant investment by the U.S. government in subsidizing electric vehicles, this is a slap in the face for not only UAW members and their families but also for U.S. taxpayers and the American workforce,” said Terry Dittes, UAW vice president and director of the General Motors Department.