As Japan looks to deflect opposition to its inclusion in a pan-Pacific free-trade pact, a Washington lobbying battle is taking shape, with a prominent D.C. law firm and the U.S. Chamber of Commerce on one side and American automakers on the other.

Japanese Prime Minister Yoshihiko Noda announced in November that his country would join discussions for the Trans-Pacific Partnership agreement, which is trying to eliminate import tariffs. The United States and eight other nations also are participating in the talks.