President Trump is threatening Mexico and the European Union, two of the largest U.S. trading partners, with 30% tariffs starting in August if they don't reach a trade deal with the U.S. CBS News MoneyWatch correspondent Kelly O'Grady breaks down what this means for U.

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.

President Donald Trump has posted two new letters on his social media platform announcing tariffs on the European Union and Mexico.

Major stock indexes were slightly lower on Friday as U.S. President Donald Trump's announcement of tariffs on imports from Canada fanned worries about trade tensions, with the Canadian dollar down against the greenback.

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.

It shows that personal grudges rather than simple economics are a driving force in the U.S. leader’s use of tariffs.

European Commission President Ursula von der Leyen said that there needed to be a “genuine rebalancing” in the China-Europe relationship.

The president also decided to send out letters as a way to keep the pressure up.