They come as the two countries, along with Mexico, are trying to hammer out a renegotiated North American Free Trade Agreement and after Trump sent a warning to Trudeau late Thursday that the days of the USA being taken advantage of in trade deals "are over".
In response, Canada announced Can$16.6 billion (US$12.8 billion) in retaliatory duties on United States goods, including potentially on beef, coffee, candies, plywood and surprisingly, maple syrup, as well as steel and aluminum. But they did not sound optimistic.
Outraged leaders from the world's major economies launched legal challenges Friday after announcing countermeasures to retaliate against harsh steel and aluminum tariffs which Trump allowed to take effect.
Sometimes, the USA will impose additional duties on foreign imports that it determines are being sold at unfairly low prices or are being supported by foreign government subsidies.
The WTO Secretariat received a request from the European Union for consultations with the United States "concerning the Section 232 tariffs imposed by the United States on steel and aluminium imports", said the official who requested anonymity. "It is entirely inappropriate to view any trade with Canada as a national security threat to the United States", she said.
Mexico complained that the tariffs will "distort worldwide trade" and said it will penalize USA imports including pork, apples, grapes, cheeses and flat steel.
Stock prices slumped amid fears of a trade war, with the Dow Jones industrial average falling almost 252 points, or 1%, to 24,415.84.
"Unilateral responses and threats over trade war will solve nothing of the serious imbalances in the world trade".
The normally harmonious group of wealthy industrial countries devolved into a "G6 plus one" as some officials put it, calling on Mnuchin to send a message of their "regret and disappointment" to President Donald Trump. California Democrats are already buying billboards in the Central Valley denouncing Trump trade policies as ruinous to state farmers.
European Commission President Jean-Claude Juncker has said the tariffs are targeted at countries not responsible for overcapacities, calling the USA duties "protectionism, pure and simple". But they can also increase costs more broadly for US manufacturers who cannot source all their needs locally and have to import the materials. That hurts the companies and can lead to more expensive consumer prices, economists say.
French Finance Minister Bruno Le Maire also expressed his anger at the meetings ended.
European officials had braced for the tariffs and the EU has threatened to retaliate against US orange juice, peanut butter and other goods in return.
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. "If we charge a country ZERO to sell their goods, and they charge us 25, 50 or even 100 per cent to sell ours, it is UNFAIR and can no longer be tolerated. It's not that we can't talk just because there's tariffs", he said.
"China's door for negotiation remains open", said foreign ministry spokeswoman Hua Chunying on Friday. He said he planned to travel to China on Friday for trade talks between the world's two biggest economies. "It's not about who attacks whom, and then wait and see who is still standing at the end".
Speaking on a panel on cooperation between countries, Ross expressed concern that the Geneva-based World Trade Organization and other global organizations are too rigid and slow to adapt to changes in business. "We are ready to rebuild this multilateralism with our American friends".
Ross and Lighthizer seem like the odd men out at this week's gathering at the OECD, an worldwide economic agency that includes the U.S.as a prominent member.