Blue-collar auto workers are getting behind U.S. President Donald Trump's latest threat against car imports, but the suits in America's car capital doubt a crackdown will come to pass.

"I welcome the fact that they're investigating this," United Auto Workers President Dennis Williams told reporters Thursday in Detroit. "The United States became a dumping ground for a lot of countries at a very low cost."

The union leader voiced his support a day after Trump teased "big news," then proceeded to order his Commerce Department to investigate whether imported cars pose a national security threat. The trade group that represents General Motors Co., Ford Motor Co. and Fiat Chrysler Automobiles NV's interests in Washington is dubious that the probe will give the president's administration cover to implement tariffs or limit imports, which would be allowed under a section of the 1960s trade law.