The U.S. Department of Commerce on Thursday set final duties on Canadian softwood lumber after finding that imports were being unfairly subsidized and dumped in the United States, escalating a trade dispute with Canada in the midst of NAFTA trade talks.

The decision imposes anti-dumping and anti-subsidy duties affecting about $5.66 billion worth of imports of the key building material.

Canada called the measures "unfair, unwarranted and deeply troubling" and said it was considering its options, including legal action through the North American Free Trade Agreement (NAFTA) and the World Trade Organization (WTO).