The auto alliance said its analysis of 2017 auto sales data showed a 25 percent tariff on imported vehicles would result in an average price increase of $5,800, which would boost costs to American consumers by nearly $45 billion annually.

Automakers are concerned tariffs would mean less capital to spend on self-driving cars and electric vehicles.

"We are already in the midst of an intense global race to lead on electrification and automation. The increased costs associated with the proposed tariffs may result in diminishing the US' competitiveness in developing these advanced technologies," the stetment wrote.

Toyota said in a separate statement on Wednesday that new tariffs "would increase the cost of every vehicle sold in the country". The automaker said the tariffs would mean even a Toyota Camry built in Kentucky "would face $1,800 in increased costs".

Both automotive trade groups cited a study by the Peterson Institute for International Economics that the cost to US jobs from the import duties would be 195,000 jobs and could be as high as 624,000 jobs if other countries retaliate.

The German Association for Small and Medium-sized Businesses said the "pattern of rising protectionism is very likely to continue if the US decided to impose tariffs on foreign automobiles and automobile parts, thus causing tremendous damage to both economies".

Alabama Governor Kay Ivey, a state that produced nearly 1 million vehicles and 1.7 million engines built by foreign automakers last year, urged the Commerce Department not to invoke the tariffs. She said job losses from new levies could be "devastating".

The proposed tariffs on national security grounds have been met by opposition among many Republicans in Congress.

But Trump has made the tariffs a key part of his economic message and repeatedly complained about the US auto sector trade deficit, particularly with Germany and Japan. Although some aides have suggested that the effort is a way to try to pressure Canada and Mexico into making more concessions in ongoing talks to renegotiate the North American Free Trade Agreement.

US Commerce Secretary Wilbur Ross said on Thursday the department aimed to wrap up the probe by late July or August. The Commerce Department plans to hold two days of public comments in July on its investigation into auto imports.

The Commerce Department has asked if it should consider US-owned auto manufacturers differently than foreign automakers.

The Association of Global Automakers rejected that contention, saying its members' American workers "are no less patriotic or willing to serve their country in a time of crisis than any other Americans".

The group questioned national security as grounds to restrict auto imports. "America does not go to war in a Ford Fiesta," they added.

The Alliance said there was "no basis" to claim that auto-related imports were a threat to national security and noted that 98 percent of US auto imports came from US national security allies.

Reuters