Economic reporter Promit Mukherjee says Canada's retaliatory tariffs on US goods are designed to put pressure on the US and President Trump, intensifying an 18-month-old trade war ▻ ↧ Canada's retaliatory tariffs take effect as US trade talks stall Canada's retaliatory tariffs on U.S. goods took effect after midnight on Tuesday, intensifying an 18-month-old trade war ​and spurring Prime Minister Mark Carney to urge a further shift away from the country's biggest trading partner.