US defense secretary Leon Panetta says that US and Japanese officials have agreed to put a second missile defense system in Japan.
The exact location has not yet been determined.
But officials stressed on Monday that the radar system is aimed at protecting the region against the threat from North Korea, and is not directed at China.
The US already has similar early warning radar systems on ships in the Asia-Pacific.
This second Japan-based system will allow ships to spread out and cover other parts of the region.