DETROIT (AP) — Ford is forming a joint venture with one of its suppliers that will build two North American factories that will make batteries for roughly 600,000 electric vehicles per year by mid-decade. The deal with SK Innovation of Korea was announced Thursday. It sets up a possible confrontation between the companies and the United Auto Workers, which issued a statement saying Ford has a moral obligation to make sure plant workers are paid union wages. The joint venture called BlueOvalSK is the start of Ford’s plan to vertically integrate key parts of the electric vehicle supply chain. The companies say they have signed a memorandum of understanding, but details on the ownership structure, factory sites and union representation have yet to be worked out.