DETROIT – The United Auto Workers union is positioning itself as a car company partner rather than an adversary as it renews a campaign to sign up workers at U.S. plants owned by foreign-based car companies.

Yet Bob King, the union’s president, said it will play tough with Toyota, Honda, BMW, Hyundai and others if they don’t agree to secret-ballot election principles that the union supports. Companies that don’t sign on to the principles will be branded as human rights violators, King told an industry group Wednesday.

The UAW has had little success over the past 30 years in organizing workers at U.S. factories owned by Japanese, Korean and German auto companies. The companies built factories mainly in southern states such as Tennessee, Alabama, Mississippi and Kentucky that are generally not as union-friendly as the UAW’s home base around the Great Lakes. Many also pay wages comparable to UAW-represented factories owned by Detroit automakers, but the foreign companies have avoided UAW rules that can make plants less efficient.

King, speaking at the Automotive News World Congress in Detroit, said the union has learned from the Detroit companies’ near-death experience and has eliminated inefficient work rules, job classifications and other issues that foreign companies have feared.

Instead, he said the union understands how globalization has made it necessary for the UAW to help auto companies make money by being more competitive.

The UAW’s membership has fallen from a high of 1.5 million in 1979 to around 350,000.