Photo: The Canadian Press

Logs are stacked at Murray Brothers Lumber Company woodlot in Madawaska, Ontario on Tuesday April 25, 2017. The United States International Trade Commission has unanimously voted that the American lumber industry has been harmed by Canadian softwood lumber imports.THE CANADIAN PRESS/Sean Kilpatrick

The federal government vowed to aggressively defend Canada's softwood lumber industry after the U.S. International Trade Commission unanimously voted that American producers have been harmed by imports of subsidized Canadian lumber.

"We will stand shoulder to shoulder with the forestry sector in Canada," Natural Resources Minister Jim Carr told reporters in Ottawa.

Carr called the duties unnecessary and said Canada has already launched challenges under both the North American Free Trade Agreement and at the World Trade Organization. The NAFTA dispute panel has to make a ruling by next fall. The WTO process could take years.

"We have fought them before and we'll continue to defend Canada's interests," Carr said.

He added the government is helping the industry by offering a support package, including loan guarantees at commercial rates, and working to expand export markets and transform the industry.

In a 4-0 vote Thursday, the agency sided with the U.S. lumber coalition, which complained that Canadian lumber was subsidized and that it was dumped into the American market at artificially low prices.

Most Canadian producers will now pay a combined countervailing and anti-dumping rate of 20.83 per cent, down from 26.75 per cent in the preliminary determinations issued earlier this year.

Canadian producers have paid about $500 million in deposits for the duties thus far.

The duties have added to the cost of building a home in the United States. Canadian unions and lumber companies fear the issue will eventually cause layoffs.

West Fraser Timber pays the highest duties at 23.7 per cent. Canfor is next at 22.13, followed by Tolko at 22.07, Resolute Forest Products at 17.9 per cent and J.D. Irving at 9.92 per cent.