Negotiators trying to clinch a Pacific Rim free trade deal made progress toward resolving a key issue on Wednesday when Canada and Mexico signaled a willingness to open the North American auto market to more parts made in Asia, people briefed on the closed-door talks said. The Trans Pacific Partnership, or TPP, which seeks to cut trade barriers and set common standards among a dozen nations reaching from Japan to Chile, has become snared over a small set of issues, including trade in autos and auto parts, since July.