U.S. President Donald Trump's top trade official says it's "unhinged" for Canadian leaders to characterize the administration's tariffs as a trade war against Canada.

Canada struck back at U.S. President Donald Trump on Tuesday with tariffs on about $20 billion worth of U.S. goods. The outcome could resonate far beyond Canada.

Jamieson Greer says the escalation was a "natural consequence" of Canada choosing "senseless retaliation" over a near-final trade deal.