OttawaCanada rejected US relief on heavy trucks.
The refusal leaves 50% tariffs intact on $20 billion in Canadian exports.
Ottawa retaliates dollar-for-dollar, not proportionally, targeting steel, dairy and electronics — sectors picked for political pain in Washington.
Counter-tariffs start September 8; Greer says Washington will take further, unspecified retaliatory steps.
Sources: CBC News, Fortune, TRT World, India Today, Al Jazeera Online