The 25% tariffs will be applied to imported passenger vehicles, including cars, SUVs, minivans, cargo vans and light trucks, according to a White House fact sheet released after Trump's Oval Office remarks. The tariffs will also be applied to key imported auto parts, including engines, powertrain parts and electrical components.

"At this time, the message thread that was reported appears to be authentic, and we are reviewing how an inadvertent number was added to the chain," the NSC said.