The Globe and Mail reports in its Wednesday edition that U.S. Trade Representative Jamieson Greer is advocating for revisions to trade rules that prioritize U.S. content in manufacturing supply chains. The Globe's Mark Rendell writes that Mr. Greer believes there could be preferential tariff rates in North America if Canada and Mexico align on external tariffs. However, he cautions that talks with Canada regarding its auto sector may be challenging. Canada has not yet started formal talks with the U.S. and won't be at the negotiating table this week in Mexico City. Mr. Greer says Canada and the U.S. continue to co-operate well across a range of commodity sectors, where trade has remained largely tariff free. These include energy, minerals and fertilizer. But he warns that discussions about Canadian manufacturing industries, particularly the auto sector, could prove difficult, given President Donald Trump's goal of bringing auto production back to the U.S. "If you're going to sell here, we want you to build here," Mr. Greer says of the auto industry. "So, I think on some of these issues it's going to be a challenging negotiation [with Canada]. But in some sectors of the economy it has been fine, and it will be fine."