Canada and Brazil are likely to bear the brunt of any tariffs on steel imposed by President Donald Trump, according to a 2017 report from the U.S. Department of Commerce.
According to the department's International Trade Administration and IHS Global Trade, Canadian and Brazilian steel comprised 16 percent and 13 percent of U.S. steel imports as of September 2017. China, frequently criticized politically for dumping cheap steel on trade partners, is not one of the top 10 importers of steel to the U.S.
In response, Canadian officials promised to respond to U.S. tariffs; Canadian Trade Minister Francois-Phillippe Champagne said the taxes would be "unacceptable," and said he'd take measures to defend the country's workers.
Source: IHS Global Trade Atlas, US Department of Commerce
Other top sources of steel used domestically include South Korea, Mexico and Russia.
President Trump announced Thursday that the United States will impose a 25 percent tariff on steel imports and a 10 percent tariff on aluminum imports as early as next week. The commander in chief has long pushed for trade deals more favorable to the U.S., arguing that numerous existing agreements put the country in jeopardy.
Top foreign sources of aluminum included Canada (56 percent), Russia (8 percent) and the United Arab Emirates (7 percent) between 2013 and 2016, according to the United States Geological Survey.
Alcoa, one of the world's largest producers of aluminum, protested President Trump's move, arguing that certain trading partners should be spared from the taxes.
"We believe vital trading partners, including Canada, should be exempt from any tariff on aluminum," Alcoa said in a statement to CNBC. "The aluminum industry has an integrated supply chain and actions should not penalize those that abide by the rules. We will continue to work on solutions that create a level playing field and address Chinese overcapacity."
Stocks fell sharply after the president's announcement as fear of a trade war sparked a broad equity sell-off on Thursday, with the Dow Jones industrial average falling more than 400 points through the close.