Mexico: Its government said it would impose "equivalent measures" on United States products - including flat steel, lamps, pork legs and shoulders, sausages and food preparations, apples, grapes, blueberries, various cheeses, and more.
"The American administration has made a decision today that we deplore, and obviously is going to lead to retaliatory measures, as it must", Prime Minister Justin Trudeau said at a news conference in Ottawa with Freeland.
She calls the US measures illegal and counterproductive.
The EU had "no choice" but to bring a case before the World Trade Organization and impose duties on United States imports, he added.
Germany's Volkswagen, Europe's largest automaker, is warning the Trump administration's decision to impose tariffs on aluminum and steel imports from Canada, Mexico, and the European Union could start a trade war that no side would win.
During a conference call early Thursday, Ross shrugged off questions about the US facing possible retaliation, or whether the move would negatively affect the G7 meeting.
New tariffs imposed by the United States have been condemned by German business and political leaders, who say a trade war will damage economic growth and prosperity.
The groups Freedom Partners Chamber of Commerce and Americans for Prosperity said the tariffs would hurt the nation's economy and low unemployment rates. Products hit by this could include American-made blue jeans, bourbon, and motorcycles. Prime Minister Justin Trudeau fired back with tariffs on $16.6-billion worth of US products, from beer kegs to pizza to coffee.
European Union trade commissioner Cecilia Malmström added: "Today is a bad day for world trade".
25 percent on imported steel and 10 percent on aluminum - and said they would take effect Friday.
Ben Digby, CBI's worldwide director, said: "These tariffs could lead to a protectionist domino effect, damaging firms, employees and consumers in the US, UK and many other trading partners".
White House National Trade Council Director Peter Navarro discusses the significance of President Trump's steel and aluminum tariffs.
The tariffs, announced by US Commerce Secretary Wilbur Ross, ended months of uncertainty about potential exemptions and suggested a hardening of the US approach to trade negotiations.
Canada and Mexico, embroiled in talks with the USA to modernise the North American Free Trade Agreement, responded swiftly.
Foreign Affairs Minister Chrystia Freeland has said Canada would retaliate if duties are imposed.
According to Navarro, the president's decision to end the exemptions is not about China or unfair trade but more about defending the US against countries who are running a large trade surplus at the expense of American jobs.
He signed-off the new tariffs surrounded by United States steel workers who are supportive of his decision. The retaliatory tariffs they've promised make no more sense in narrow economic terms than the US tariffs they're objecting to.