Trump's tariff threats

On February 1st, U.S. President Donald Trump said he would impose 25% tariffs on imports from Canada and Mexico and 10% tariffs on China, effective immediately. However, just two days later, the U.S. President announced he would pause the tariffs for 30 days after Mexico and Canada agreed to take steps to tighten border security and drug trafficking. How will Trump's policy flip-flops affect the U.S. economy? What is the real intention behind Trump using tariffs as a bargaining tool?