President Donald Trump announced tariffs of 25% on goods from Japan and South Korea beginning on Aug. 1, as he moved to impose unilateral rates on countries that have not yet secured trade deals with his administration.

President Donald Trump cranked up the pressure on two of America’s key trading partners, Japan and South Korea, firing off letters Monday to the heads of their countries that informed them of their new tariff rate.

The tariffs on some of America’s closest allies would go into effect Aug. 1, unless the countries reach some kind of trade agreement with the United States.