Senior U.S. lawmakers from both political parties have urged the Obama administration to go slow, consult with Congress and get the right deal in talks underway in Atlanta on a 12-nation Pacific Rim free trade deal. "We urge you to take the time necessary to get the best deal possible for the United States, working closely with us," said a letter and addressed to U.S. Trade Representative Michael Froman and Treasury Secretary Jack Lew. The letter marked a reassertion of congressional concern about the Trans-Pacific Partnership (TPP) deal. Congress in June gave President Barack Obama "fast track" power to push ahead with the negotiations after a six-week congressional battle. It was signed by House Ways and Means Committee Chairman Paul Ryan of Wisconsin and Senate Finance Committee Chairman Orrin Hatch of Utah, as well as the senior Democrats on those two committees, Representative Sander Levin of Michigan and Senator Ron Wyden of Oregon. The lawmakers appeared to be concerned the U.S. delegation should not assume Congress will back any deal reached and urged more "consultations and coordination" with Congress. Negotiators trying to clinch a TPP deal made headway on Wednesday over how to remove a stumbling block and give automakers a freer hand to sell cars in the United States with more parts purchased in Asia. People briefed on the closed-door talks said Canada and Mexico signaled a willingness to open the North American auto market to more parts made in Asia, one of the key hurdles to sealing a broader deal on the TPP. The TPP seeks to reduce trade barriers and set common standards among a dozen nations reaching from Japan to Chile, but talks have become snared over a small set of issues, including dairy trade and patent periods for biologic drugs.