The United Auto Workers union is petitioning the National Labor Relations Board to hold an election at a Kentucky battery plant run by a Ford Motor joint venture, the union said in a release Wednesday.

The Kentucky autoworkers, who want to join the United Auto Workers, filed for a union election Tuesday, a key development in the union’s campaign to organize Southern auto-factories and EV battery facilities.

The United Automobile Workers union asked a federal labor regulator to conduct an election at a factory Ford jointly owns with a South Korean battery company.

Workers at a Ford Motor Co. joint-venture battery plant in Kentucky have formally asked the federal government to hold a vote on joining the United Auto Workers, the union said.