Mr. Trump announced last week that vehicles and auto parts imported into the U.S. will be subject to a 25% tariff rate. The auto tariffs are expected to go into effect at midnight, just hours after the latest round of tariff announcements by the president Wednesday afternoon.

The president's long-awaited tariff announcement will come on the same day Trump faces a possible rebuke from the Senate. Enough Republicans are expected to join Democrats on Wednesday in voting to end the emergency declaration enabling tariffs against Canada.

Few details of the announcement are known prior, creating anxiety among the business community and global leaders.