TORONTO (AP) — Some Canadian officials on Tuesday blasted President-elect Donald’s Trump’s threat to impose sweeping tariffs, as the leader of the country’s most populous province called Trump’s comparison of Canada to Mexico “the most insulting thing I’ve ever heard.”

The president-elect’s opening salvo in trade and border talks with the United States’ neighbors is casting a harsh light on the North American alliance.

Mexico and Canada are the United States’ top two trading partners, accounting for nearly 30% of trade volumes.