Shares in Asian automakers also dropped overnight as companies including Toyota, Nissan, Honda and Mazda, who also have factories in Mexico, were hit by the threat.
Trump said he would hit goods coming from Mexico with a 5 percent tariff and would hike that levy each month until it hits 25 percent on Oct. 1, unless Mexico takes immediate action against illegal immigration across the U.S. border.
An auto industry source said the situation was puzzling in that the migration issues belonged to the political stage and came despite an update to the North American Free Trade Agreement (NAFTA) in the making for this summer.