SEOUL—Hyundai Motor Co.’s labor union has warned that the 25 percent automotive tariffs being considered by President Donald Trump could jeopardize 20,000 factory jobs in Alabama.

The Associated Press reports that the U.S.-based jobs would be the most vulnerable due to a labor agreement that requires the Korean automaker to close any foreign plants before ones at home. The labor union warned that a decline in U.S. auto imports connected to the Trump’s proposed tariffs could force Hyundai to examine the extent of its operations at its Alabama-based manufacturing plant.