The door to trade negotiations with the United States is closed for the moment, EU Trade Commissioner Cecilia Malmstrom said, following the US imposition of import tariffs on steel and aluminium from the European Union.
They warned that it would be met with retaliatory countermeasures.
"This is the strongest trade action Canada has taken in the post-war era", Foreign Affairs Minister Chrystia Freeland told a news conference Thursday.
He also told French President Emmanuel Macron of the need to "rebalance trade with Europe", the White House said.
Macron spoke with Trump Thursday night and called the tariffs "illegal" as well as a "mistake", according to a readout released Friday by the Élysée Palace.
The lesson to be learned by Canadian industry is that the disputes aren't about fact, subsidy or national security, said Susan Yurkovich, president of the BC Lumber Trade Council.
The Canadian tariffs, which Foreign Minister Chrystia Freeland said are proportional to the USA duties, will be applied to USA steel and aluminum as well as consumer products from July 1.
The U.S. administration also launched a national security investigation last week into auto and truck imports, using the same 1962 law it has applied to curb incoming steel and aluminum."The Trump administration seems to regard overt threats, including tariffs and repudiation of previous agreements, as a key element for gaining leverage in trade negotiations", said Eswar Prasad, a former head of the International Monetary Fund's China division and now a professor at Cornell University.
A previously published list of American products that could face European Union tariffs includes items with symbolic meaning, such as Kentucky bourbon, motorcycles and blue jeans.
"But, it would be a great pity if we ended up in a tit-for-tat trade dispute with our closest allies".
Asked if the United States was isolated on the issue of tariffs in the G7 talks, Dombrovskis said: "Indeed".
"We are heading for a trade war, which is going to be all losers - there will be no winners".
The key difference between then and now, European trade experts say, is tone.
"The most likely outcome ... could be protracted negotiations during which both the U.S. and the European Union lock horns but do not take ever more dramatic headline-grabbing protectionist steps", Schmieding said.
"Now, that side communication isn't happening".
The move, revealed by Commerce Secretary Wilbur Ross, will affect several key USA allies - and North Atlantic Treaty Organisation members - in Europe.
In much of Western Europe, there is also the lingering memory of the "freedom fries era", when U.S.
Public companies may feel pressure from shareholders who would expect them to fight the US government in court and get an injunction, he said in an interview. But the Iraq War represented a policy disagreement, political analysts note.
"These tariffs are an affront to the long standing security partnership between Canada and the United States, and in particular, an affront to the thousands of Canadians who have fought and died alongside their American brothers in arms", he said, noting the USA national security justification for its measures.
"This is protectionism, pure and simple", said Jean-Claude Juncker, president of the European Commission. "The United State will agree to a fair deal, or there will be no deal at all", Trump said. "We are ready to rebuild this multilateralism with our American friends", he said. "Let's not break completely with America, because this is not America".
In 2003, he said, the prevailing perception was that the American people supported Bush's decision to invade Iraq, given the experience of the 9/11 terror attacks.