The Mexican measures target pork legs, apples, grapes and cheeses as well as steel - products from USA heartland states that supported Trump in the 2016 election.
"We have to believe that at some point their common sense will prevail".
Mexico said it would apply penalties to blueberries, pork bellies, grapes and certain types of steel. The EU, Canada and Mexico together account for about 40 percent of USA steel imports.
Tata Steel, which employs 8,500 people across the United Kingdom, has called for "swift and robust action" in response to the steel tariffs.
However, after early negotiations, the European Union was able to negotiate a temporary exemption until June 1.
"I don't know if it's officially a "war" yet, but it's getting to be a pretty intense trade skirmish", one trade expert said.
Now, both of those men have left the White House, and Trump has gravitated instead toward seeking the counsel of trade hard-liners such as Commerce Secretary Wilbur Ross, senior adviser Peter Navarro, and U.S. Trade Representative Robert E. Lighthizer.
On NAFTA, Ross said there was "no longer a very precise date when they may be concluded and therefore (Canada and Mexico) were added into the list of those who will bear tariffs".
Trump has said the tariffs were necessary to protect USA national security, but they were widely criticized by foreign leaders, US business groups and even some labor groups as being ill designed and potentially damaging to the US economy.
"We expect immediate retaliation from the European Union, which, on a net basis, to us serves no positive economic goal", KeyBanc analyst Philip Gibbs said in a note.
The EU had "no choice" but to bring a case before the World Trade Organization and impose duties on United States imports, he added.
Stocks in the U.S. fell as the administration ignored the pleas from business lobbying groups including the U.S. Chamber of Commerce to forego tariffs.
Republican Kevin Brady, who shepherded last year's tax cut through Congress and chairs the House Ways and Means Committee, called on the administration to reinstate the exemptions. Orrin Hatch, R-Utah. The conservative Koch brothers network' also said it opposed the tariffs. "They're critical for national security".
"It's entirely up to U.S authorities whether they want to enter into a trade conflict with their biggest partner, Europe", Le Maire told reporters after the meeting.
Beyond semantics, Alden said the decision to impose tariffs would cause major economic disruptions across Europe and North America. Accordingly, despite the historical precedent for unilateral, protectionist trade measures to result in a weaker US Dollar, market participants are seemingly unmoved by the latest developments.
In a clear reference to Trump, Macron added: "These solutions might bring symbolic satisfaction in the short term. So, I think immediately it's going to clog up the borders tonight".
While China is seen at more risk from a trade war as its exports are larger than its imports from the US, the operations of American companies in China make substantial sales there, which could be hit by any turn in sentiment.