Unifor national president Lana Payne is urging Ottawa to stand firm for a good deal with the United States as a review of their free trade pact looms next year.
Payne says she's troubled by those in the business community who have pushed to reach trade deals quickly.
She says Canada has leverage in these talks and it's important to play hardball in not allowing tariffs to be legitimized in any form.
Prime Minister Mark Carney said last week that Canada and the United States will enter into formal discussions in January.
Washington's trade representative says the upcoming review of the free trade deal will hinge on resolving concerns about Canadian policies on dairy products, alcohol and digital services.
Canada has also been in talks with the U-S on sectoral tariffs that have hit industries like autos, forestry and metal production especially hard.