General Motors Co. warned Friday that the Trump administration’s proposed automotive tariffs may curb sales worldwide, forcing the iconic American carmaker to cut production and lay off workers.

GM’s statement, filed in response to a Commerce Department investigation of whether auto duties are needed to protect national security, reflect broad concern from business and lawmakers in the president’s own party that the White House’s protectionist trade policies will undermine the U.S. economy. Levies imposed on steel and aluminum imports, also on national security grounds, have already prompted retaliation from long-time U.S. allies like Canada and Europe and spurred motorcycle-maker Harley Davidson to move some production outside the U.S.