An FTA between Korea and the U.S. was established on June 30th, 2007, and it came into effect on March 15th, 2012 after some renegotiations. As a result, Korean exports to the U.S. is expected to increase, while Japanese exports to the U.S. is expected to decrease. In response, the Japanese government wants to participate in TPP(Trans Pacific Partnership) talks which are led by the U.S. However, the Japanese government needs to earn the agreements of the American administration and congress in order to participate in the TPP negotiations. To earn the agreements, Japan has to convince the U.S. in pending issues between the two countries regarding commodities such as automobile, beef, and insurance. In this research, I analyze the motives of the U.S. in carrying forward the Korea-U.S. FTA and the strategy of the U.S. in the U.S.-Japan negotiations. I also discuss the impact of the Korea-U.S. FTA on the relationships among Korea, U.S. China, and Japan. Lastly, I present how Korea should carry out its foreign policy.