Some of the media in China have intended to emphasize that the South China Sea is its core interest, which has prompted the United States to take a tougher stance on the issue of the South China Sea. The United States has changed its non-involvement and neutral position on this issue. It has stressed that ASEAN and China should sign a ”Regional Code of Conduct for the South China Sea,” and the United States intends to act as mediator. The United States has also strengthened military cooperation with Vietnam and Cambodia, and has held joint military exercises with Vietnam in the South China Sea. It seems that the United States has resumed a strategic posture in regard to the containment of China. However, since the relations between the United States and China have become closer than ever before, containment is not as effective as it was before. The tussle in the South China Sea was originally limited to ASEAN and China. However, the United States has suddenly become involved, and is expected to strategically maneuver in this area.