U.S. administration officials escalated President Donald Trump’s criticisms of Canadian Prime Minister Justin Trudeau and the global trading system on Sunday, heightening tensions with major allies as Washington enters an important stretch of negotiations on several fronts, from China to the North American Free Trade Agreement.
After the Group of Seven industrialized nations summit ended Saturday in Canada with a joint communiqué stressing the importance of a rules-based international trading system, a spat erupted between...