US stock futures fell as President Trump threatened stiff tariffs on imports from more than a dozen countries and delayed the return of sweeping April levies.

U.S. stocks are sharply lower on Monday after a three-day holiday break as investors keep an eye out for more trade-related developments.

The newest countries to be affected with Trump's Aug. 1 tariffs include Malaysia, Kazakhstan, South Africa, Laos and Myanmar. Trump shared letters that were sent to the nations, notifying them of levies ranging from 25% to 40%. They come on top of 25% tariffs imposed on Japan and South Korea.