While Mexico was spared from Trump's so-called "Liberation Day" tariff rollout on April 2, the 30% rate for the E.U. is 10% higher than what the president said he would apply to America's largest trading partner in April.

President Donald Trump posted letters to the leaders of Mexico and the European Union, saying they had not done enough to head off the new tariffs.

Mexico did not face a new tariff on April 2, the day of Trump's so-called "Liberation Day" tariff rollout. There remains a 25% tariff on non-USMCA-compliant goods from Canada and Mexico, as well as a 50% tariff on steel, aluminum and derivative products.

President Trump threatened a significant tariff hike on the European Union and Mexico, two of the largest U.S. trade partners, on Saturday. NBC News’ Yamiche Alcindor has more.

The European Union braced on Friday for a possible letter from U.S. President Donald Trump outlining planned duties on the United States' largest trade and investment partner after a broadening of his tariff war in recent days.

President Trump said he plans to impose blanket levies of 15% to 20% on most trading partners that haven't yet received suggested tariff rates. That would be higher than the 10% baseline currently in effect.