President Donald Trump signed a proclamation Wednesday instituting a 25% tariff on imported vehicles and certain auto parts in a move that will increase the cost of new vehicles. The vehicle duty is set to take effect on April 3, the auto parts piece by May 3.

Trump justified the hefty duty by findings of a 2019 commerce secretary report during his first term that found the volume of vehicle and auto parts imports threatened national security. He said the threat has only increased since the report and that trade inequities also threaten U.S. industry.

The proclamation said renegotiated trade agreements with Canada and Mexico and South Korea, three of the half a dozen countries the U.S. gets most of its imported autos and auto parts from, haven’t “yielded sufficient positive outcomes.”

The new tariff will be on top of existing duties, presumably including the new 25% tariff on goods from Canada and Mexico, though there is an exception in the latter tariff for goods that comply with the U.S. trade agreement with those countries excepting their components not made in the U.S. 

The tariff comes after nearly a month of back-and-forth tariff moves by the White House that have left many in the auto industry and beyond confused and anxious about how trade conditions will settle out and how the outcome will affect business. 

Cox Automotive adjusted its full-year new auto sales forecast Wednesday to reflect an expected slowdown, lowering its projection from 16.3 million units to 15.6 million, below last year’s 16 million in sales. It cited continued affordability challenges, economic uncertainty and potential higher inflation due to the tariffs.

One market watcher estimated that tariffs on goods just from China, Canada and Mexico would impact nearly 20% of autos sold in the U.S.

The Biden administration, for national security purposes, banned the sale of connected vehicles here that use technology from China and Russia.