U.S. Commerce Secretary Wilbur Ross said on Saturday that threats of retaliatory trade actions from Canadian officials "are inappropriate" and will not influence final U.S. import duty determinations on Canadian softwood lumber. "We continue to believe that a negotiated settlement is in the best interests of all parties and we are prepared to work toward that end," Ross said in a statement issued by the Commerce Department. On Friday, Canadian Prime Minster Justin Trudeau said his government would study whether to stop U.S. firms from shipping thermal coal from ports in the Pacific province of British Columbia in response to the lumber duties.

Wilbur Ross, U.S. Secretary of Commerce. Katie Kramer | CNBC

Canada also is considering duties on exports from Oregon such as wine, flooring and plywood, a source close to the matter told Reuters, citing the role played by U.S. Senator Ron Wyden, an Oregon Democrat, in pressing for the lumber tariffs. Trade relations between the United States and second-largest trading partner Canada have soured since the Commerce Department in late April imposed preliminary anti-subsidy duties averaging 20 percent on Canadian softwood lumber imports. The long-running dispute centers on U.S. lumber producers' charges that lower-cost Canadian competitors benefit from an unfair government subsidy because Canadian timber is mostly grown on public lands.