Rio Tinto Group, one of the world’s largest aluminum producers, runs a refinery and five smelters in Canada’s Quebec province, with most of the metal flowing south to the US market.

Now, with President Donald Trump’s tariffs, it’s suddenly cheaper for Rio to buy aluminum in the US and resell it to American customers rather than move its own metal across the border.

Trump’s 50% tariff on aluminum imports, which took effect in June, forced Rio to curb shipments to the US and instead buy supplies from rivals - as long as those supplies are already in the country. The shift in strategy was described by people familiar with the move who asked not to be identified discussing sensitive commercial matters.

Trump casts his tariffs as necessary to protect American industries, and they are already

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