We begin here in Washington, where President Trump's plan to impose tarrifs on Mexico has created widespread concern that the US economy and American consumers will pay the price. It's also sent stocks sliding. The Dow Jones lost nearly one and a half per cent. Trump's motivation is to get Mexico to stem the flow of migrants crossing the US border illegally. But his advisers reportedly fear that the move could jeaporadize the new US-Mexico-Canada Trade Agreement. Our North America correspondent Jon Brain has more.