President Donald Trump told reporters in the Oval Office on Friday afternoon that tariffs on car imports to the U.S. would start “maybe around April 2.” He added that he decided not to start them on April 1 because, “I’m a little suspicious,” referring to April Fools’ Day.

Car tariffs may start in April.

Trump didn’t specify which car imports would be affected. Mexico, Japan, Canada, and South Korea import the most cars to the United States. Millions of cars sold in the U.S. each year are assembled in Mexico and Canada alone.

Ford CEO Jim Farley said earlier this month that tariffs “would have a huge impact on our industry with billions of dollars of industry profits wiped out.”

On Monday, Trump signed an executive order imposing 25% tariffs on imports of steel and aluminum, causing shares of car makers General Motors, Ford, and Tesla to fall. Because auto makers use some imported metals to make their cars, the tariffs could lead to higher car prices for consumers. Those tariffs will take effect on March 12.

The president has announced tariffs in the past that have not taken effect. In January, he walked back 25% tariffs on goods from Mexico and Canada after both countries agreed to stronger border controls.

He has followed through on other tariff announcements, including the additional 10% tariffs on Chinese goods, which took effect earlier this month. China responded by imposing tariffs ranging from 15% on U.S. imports of coal and liquefied natural gas, to 10% on crude oil, agricultural machinery, pickup trucks, and some cars.

Shares of GM, Ford, and Tesla closed either flat or slightly higher on Friday.