Canada has filed an expansive complaint with the World Trade Organization, accusing the US of breaking international trade rules.
The complaint challenges the ways the US investigates products for subsidies and below-cost sales in the US.
The US called the claims “unfounded”.
The action comes amid disputes between the two countries over issues such as dairy, aircraft sales and lumber as well as tense efforts to renegotiate the North American free trade deal.
Canada’s 32-page complaint cites US investigations of products from countries around the world, with decisions that date back to 1996.
Among other charges, Canada says the US improperly calculates rates and restricts parties from presenting evidence to defend themselves, with a cut-off for supplying information that comes too early in the process.
It also accuses the US International Trade Commission of being biased, since disputes over which the body’s six commissioners are evenly divided automatically result in a finding.
The complaint targets a process that the US has deployed frequently under President Donald Trump, who has embraced a protectionist stance on trade.
The US Commerce Department launched more than 80 antidumping and countervailing duty investigations last year – a 46% increase from 2016.
The investigations, which are typically triggered by complaints from private companies, can lead to steep tariffs.
This week, the Commerce Department announced results in other investigations – including one against Canadian newsprint producers.
US Trade Representative Robert Lighthizer called the complaint “a broad and ill-advised attack on the US trade remedies system”.
He said: “Canada’s claims are unfounded and could only lower US confidence that Canada is committed to mutually beneficial trade.”
Canada filed the petition with the WTO on 20 December. It was shared with the organisation’s members on Wednesday.
The complaint allows for 60 days of “consultation”. If it is not resolved in that time, it is subject to adjudication by a WTO panel.