A spokesperson for China’s Foreign Ministry said on Wednesday that the U.S.’ 25 percent tariffs on all steel and aluminum imports seriously violate WTO rules, severely undermine the rule-based multilateral trading system, and are not conducive to solving its own problems.

U.S. President Donald Trump on Monday U.S. time signed proclamations raising tariff rates on steel and aluminum imports to 25 percent from all countries, which would take effect on March 4, according to Reuters.

Asked to comment on the move, Guo Jiakun, the spokesperson for the Chinese Foreign Ministry, stressed that “protectionism leads nowhere, and trade and tariff wars have no winners.”