Indonesia,. as an archipelagic state, Indonesia relies on United Nations Convention on the Law of the Sea (UNCLOS) 1982 to preserve its territory. Unfortunately, there are so many problems that Indonesia has to face in the water territory. In this interdependency era, Indonesia also makes some cooperations with other state to overcome the problems that Indonesia has to face, especially with United States. Unfortunately, United States doesn’t ratify the UNCLOS which makes the position of Indonesia as an archipelagic state is unclear to the government of United States. This writing tries to examine the reason why Indonesia wants to make cooperation with US, a state which does not ratify the UNCLOS. The research method for this writing uses library research. The result of the research shows some reasons like the need of Indonesia to a maritime security, economics, preserving natural resource, fishery conservation, and technology.