The United States’ 25 percent tariffs on imports from Canada and Mexico and its additional ten percent tariff on Chinese imports went into effect at 12:01 a.m. Tuesday, Eastern Standard Time.

The tariffs, which U.S. President Donald Trump linked to border security issues, including a crackdown on drug trafficking, are seen as the beginning of a “tariff war” between the U.S. and its neighbors and potentially the second round of a U.S.-China trade war.

On Monday, Trump confirmed that there was no room for negotiations on the tariffs against Canada and Mexico.

Trump also signed an executive order on Monday imposing the additional ten percent tariff on China, bringing U.S. tariffs on China to a total of 20 percent.