The US is lifting some of its 50% tariffs on Canadian goods, with the White House saying on Friday it was working to "protect the economic prosperity and national security of the American people".
The exemptions could also boost Republican candidates in the midterms elections on 3 November, as many US voters list affordability and economic pressures as top issues.
Republican Senator Susan Collins, who is in a tight race in Maine to keep her seat in the election, first announced the exemptions, saying they would help her state's agriculture industry.
After trade talks collapsed this summer, the US and Canada started an escalating tariff war that has affected both sides of the border.
Senator Susan Collins said she had worked with the administration to secure "tariff relief"