TORONTO — The United States is banning the import of some dairy products and motorcycles from Canada along with most alcoholic beverages, the White House said Tuesday, as part of a trade war that shows little sign of cooling off. The ban will take effect Sept. 29 and comes after retaliatory tariffs promised by Canada kicked in earlier Tuesday on $20 billion in U.S. imports. Canada had responded to tariff moves by U.S. President Donald Trump after trade talks between the countries broke down last month. Trump also moved to shut Canadian products out of large, long-term U.S. government contracts and directed the U.S. General Services Administration to declare Canadian products ineligible for those contracts until Canada allows “full and fair reciprocity″ for American products. Canadian Prime Minister Mark Carney said Canada’s strategy was about becoming more independent and vowed to speed those efforts. “It’s about ensuring that no country can hold us hostage. And that we can live how we want to live," he said. The rupture has upended one of the world’s closest relationships.