President Donald Trump's trade war with Canada is escalating as the midterm elections approach, threatening Republican efforts to address voters' economic concerns in a year when control of the U.S. Senate hinges on states along the border between the United States and its northern neighbor.

Canada struck back at the United States on Tuesday with retaliatory tariffs on about $20 billion worth of American goods, including steel, dairy products, appliances and farm equipment, as the trade war between the once-friendly neighbors escalated sharply.

The trade war between the U.S. and Canada is intensifying after negotiations broke down over the weekend. Canadian Prime Minister Mark Carney said his country had been preparing for a fundamental shift in its relationship with the U.S., which it no longer views as a reliable partner. Geoff Bennett discussed the economic fallout on both sides of the border with Peter Armstrong of the CBC.

Canada will announce retaliatory tariffs against the United States on Tuesday, an official familiar with the plans told The Associated Press, escalating a trade fight that has sharply worsened since negotiations with the Trump administration collapsed.