President Trump announced 30% tariffs on the European Union and Mexico, effective August 1, if they do not negotiate better terms.
Trump has been sending out letters to countries this week, adjusting proposed tariff levels from April and encouraging further negotiations.
The EU's hopes for a tentative deal with the US were dampened by Trump's letter, which emphasized the need for open market access.
In his letter to Mexico, Trump criticized the country for not doing enough to stop drug cartels from turning North America into a 'Narco-Trafficking Playground.'