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.

It didn't take long for the European Union, Canada, and Mexico to hit back at the US after the Trump administration announced on Thursday that the three key allies would soon be subject to steel and aluminum tariffs.

The countries 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," he said.

French President Emmanuel Macron called the move illegal. Steffen Seibert, a German-government spokesman, also called the tariffs "unlawful."

"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."

The EU, Canada, and Mexico 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. Yet all three key trading partners insisted that they pose no national security risk to the US and ought to be exempt from the restrictions.

Here's a rundown of the announced or expected countermeasures from the US allies: