"This is stupid. It's counterproductive", former British trade minister Francis Maude told BBC. "Any government that embarks on a protectionist path inflicts the most damage on itself".
The French official expressed hope that the discussion will lay the foundation for successful talks during next week's summit of G7 national leaders in Quebec's Charlevoix region.
Tariffs of 25 per cent on steel imports and 10 per cent on aluminium were imposed on the EU, Canada and Mexico from midnight in Washington. Trade war fears drove Chinese shares lower on Friday, with the Shanghai Composite Index ending down 0.7 per cent.
That meeting, which will be hosted by Canadian Prime Minister Justin Trudeau, will be Trump's first visit to Canada as president.
Mr Trump yesterday blasted Canada after Ottawa hit back with retaliatory duties on United States imports worth up to C$16.6 billion (S$17 billion).
"That Canada could be considered a national-security threat to the United States is inconceivable".
Trudeau earlier deplored a decision by Trump to impose tariffs on steel and aluminum imports. "People have no idea how badly our country has been treated by other countries".
Weissman said most companies have some breathing room because of hedging contracts that protect them from wild price swings.
The EU has already issued a 10-page list of tariffs on United States goods ranging from Harley-Davidson motorcycles to bourbon.
Cecilia Malmstrom, the European Union trade commissioner, announced the European Union would be seeking to implement a number of retaliatory tariffs on American products by June 20.
European Union foreign policy chief Federica Mogherini said Friday: "We are living in times of geopolitical turbulence, and uncertainties, so the cooperation between European Union and China becomes even more important".
The US tariffs coincide with - and could complicate - the Trump administration's separate fight over Beijing's strong-arm tactics to overtake US's technological supremacy.
The world's two biggest economies have threatened to impose tariffs on up to $200 billion worth of each other's products.
On Thursday, Trudeau hit back at punishing United States tariffs on steel and aluminium with Can$16.6 billion (US$12.8 billion) in duties on USA goods, and accused American President Donald Trump of lacking "common sense". An official at the WTO said the body had received a request from the European Union for consultations with the United States concerning the tariffs on steel and aluminum.
"As to Canada, Mexico, you will recall that the reason for the deferral had been pending the outcome of the NAFTA talks", he said.
"We think that the G7 (meetings) will be useful if at the end of the G7, the United States is aware of the possible negative consequences of their decision on the unity of the G7 - not only the economic unity, but also the political one", Mr Le Maire said. He also launched the largest trade action that Canada has taken in eight decades. But the two sides could not reach an agreement.
Faced with thin margins, automakers will have to make a hard choice: Pass along the 25 per cent tariff on steel and 10 per cent rate on aluminum and risk getting stuck with inventory, or absorb the increases and reduce profits, said Flavio Volpe, president of the Automotive Parts Manufacturers' Association. They report a really high surplus on trade with us.
It's unknown if Ottawa will offer its own package as it did by offering lumber companies loans and loan guarantees as part of its $867 million Action Plan to help smaller lumber producers deal with the tariffs.
"We need trade policies that are fair to American workers, environmentally sound, and good for American business, but starting a trade war with our closest allies is the worst thing we could do".