TORONTO -- Finance Minister Bill Morneau says Canada should be exempted from the aluminum and steel tariffs U.S. President Donald Trump is weighing.

He says Canada is a "staunch ally" of the U.S. and that it has been "firm" in its opposition to the tariffs.

Speaking at a women's entrepreneurship event in Toronto, he stressed the tariffs are not advantageous to either country or national security.

Morneau's comments came hours after Trump tweeted he would nix aluminum and steel tariffs if NAFTA negotiations end with a new agreement that's more favourable for the U.S.

The latest round of NAFTA talks are concluding this week in Mexico City.

The Trump administration has been citing national security as the reason why it's eyeing tariffs of 10 per cent on aluminum and 25 per cent on steel.