Mexico has become the latest country to take the United States to the World Trade Organization over Washington's steel and aluminum tariffs.
Mexico's economy ministry said Monday it was starting the dispute settlement process because the U.S. was violating WTO rules.
Washington imposed a 25 percent tariff on steel imports and 10 percent tariff on aluminum imports from Mexico, Canada and the EU last week.
Ottawa and Brussels have already filed complaints with the WTO and all three nations have announced retaliatory measures against American goods.
The EU also said it could impose preliminary measures to safeguard its steel and aluminum industries as early as next month.
Meanwhile, President Trump took aim at China and Canada again in a series of tweets on Monday.
He said China's taxing on American soybeans and Canada's trade barriers on agricultural product were not acceptable.