"Other trading partners observing these threats will have the same mistrust of the negotiation process," experts argue.

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 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 on Saturday threatened duties of 30% on products from Mexico and the European Union, two of America’s biggest trading partners, in an ongoing tariff campaign that’s upended global trade since he retook office in January.

President Donald Trump said he would send letters to more than 150 countries notifying them of tariff rates as he pushes ahead with a trade agenda that has sent US partners racing to avoid higher import taxes.

U.S. President Donald Trump said he believed Britain would fight to defend the United States but suggested he could not say the same for the European Union, a factor in his decision not to sign a trade deal with the bloc.