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.

Futures attached to the Dow Jones Industrial Average (YM=F) and the benchmark S&P 500 (ES=F) fell 0.2%. Future attached to the tech-heavy Nasdaq 100 (NQ=F) slipped 0.1%.

On Monday, stocks fell as Trump posted to Truth Social letters addressed to the leaders of 14 countries threatening 25% to 40% tariffs starting August 1. Key US trading partners Japan and South Korea were among the group, as well as Malaysia, South Africa, and Indonesia.

The president also signed an Executive Order Monday officially moving his July 9 deadline for the resumption of “Liberation Day” tariff rates to August 1.

Read more: The latest on Trump’s tariffs

“The President may send more letters in the coming days and weeks,” a statement from the White House said.

In an early response to a tariff letter, South Korea said it would kick trade negotiations with the US into high gear, adding that it considered the new date an extension of a grace period.

Other than on the trade, Wall Street expects a quiet week in terms of economic releases and earnings. Minutes from the Federal Reserve’s June meeting land Wednesday, and Delta (DAL) kicks off earnings season Thursday.