The president-elect’s threat to hit Canada, Mexico and China with new tariffs is already rocking business and diplomatic relationships and could topple the trade pacts he signed in his first term.

“Right now, I see everything that Trump’s doing on tariffs as a negotiating tool,” said Sen. Chuck Grassley (R-Iowa), who saw farmers in his home state negatively impacted by retaliation from Trump’s first trade war with China. “And we’ll have to wait and see how successful he is about that.”

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.

All it took was a single social media post by Donald Trump for world leaders to plunge into response mode, US automaker stocks to tumble and investors to begin scrambling to assess potential economic impact.

With a Monday evening promise on Truth Social that his incoming administration will slap 25 percent tariffs on all goods from Canada and Mexico — as well as increasing already existing tariffs on China — Trump sent reporters (and investors,

U.S. oil and gas lobbying groups said on Tuesday they were wary of President-elect Donald Trump's threat of tariffs on Canada and Mexico, saying such policies could affect consumers, industry and security.