President Donald Trump announced that the European Union, Canada, and Mexico would soon be subject to steel and aluminum tariffs.
The decision angered the three key trading partners.
EU leaders promised to retaliate with tariffs on US goods.
Mexico's economy ministry said pork, steel, and other US products would be subject to tariffs.
The three allies lambasted the US decision, calling the move a violation of trade rules and a breakdown of international cooperation.
Canadian Prime Minister Justin Trudeau said the steel and aluminum tariffs were "totally unacceptable" and a violation of a centuries-old relationship between the US and Canada.
"These tariffs will harm industries and workers on both sides of the Canada-US border and will disrupt supply chains that have made North American steel more competitive across the globe," Trudeau said.
European Commission President Jean-Claude Juncker said Trump's tariffs were "totally unacceptable" and promised to retaliate in due course.
"This is a bad day for world trade," Juncker said.
French President Emmanuel Macron called the move illegal. Steffen Seibert, a German-government spokesman, also called the tariffs "unlawful."
More on Trump and Macron's relationship:
"This measure brings the danger of a spiral of escalation, which in the end harms everyone," Seibert said in a statement.
The Mexican economy ministry also related the country's displeasure with the new crackdown: "Mexico profoundly regrets and condemns the decision by the United States to impose these tariffs on imports of steel and aluminum from Mexico."
All three allies took umbrage with the US's justification for the tariffs. The Trump administration is using an obscure section from a half-century-old trade law to impose the tariffs on national-security grounds. All three of the key trading partners insist that they pose no national security risk to the US and should be exempt from the restrictions.
Here's a rundown of the announced or expected countermeasures from the US allies:
Mexico: Its government said it would impose "equivalent measures" on US products — including flat steel, lamps, pork legs and shoulders, sausages and food preparations, apples, grapes, blueberries, various cheeses, and more.
EU: Juncker said the bloc would move forward with tariffs on equal value to the steel and aluminum measures. The EU had previously released a list of US products that would be subject to tariffs in the event the metal restrictions went into effect. The list included blue jeans, motorcycles, boats, bourbon whiskey, rice, playing cards, and steel.
Canada: Foreign Minister Chrystia Freeland told reporters that Canada would impose retaliatory tariffs on US goods including steel, aluminum, and more — up to a value of $6 billion. According to Freeland, the tariffs were the "strongest action by Canada in the post-War era." In addition to the industrial metals, the Canadian tariffs would apply to some consumer products, such as maple syrup, pizza, and toilet paper.