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

Markets are seeking clarity on President Trump's tariffs, with the president targeting Aug. 1 for new country-specific tariffs.

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.