Financial markets, which have shown increasing insensitivity to tariff threats from the US, will face a test at the Monday open after President Donald Trump declared a 30% rate for the European Union and Mexico effective Aug.

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.

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

Trump slapped a 50% tariff on Brazil, and Brazilian President Luiz Inacio Lula da Silva said his country would respond.

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

President Donald Trump posted several more letters on social media on Wednesday, setting tariff rates ranging from 20% for products from the Philippines to 30% for products from Algeria, Iraq, Sri Lanka,

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