WASHINGTON - The United States is in discussion with Japan about expanding its missile shield in the Asia-Pacific region, Chairman of the Joint Chiefs of Staff Martin Dempsey said Thursday.

In a Pentagon press briefing with visiting Japanese Self Defense Forces Chief of the Joint Staff Shigeru Iwasaki, Dempsey said he discussed with Iwasaki about deploying another early-warning radar to Japan to bolster missile shield in Asia.

"On the issue of Missile Defense in general, we are very closely partnered with the Japanese partners," said Dempsey, noting the US side already has one X-band radar in northern Japan.

"No decisions have been taken to expand that capability, but it's certainly a topic of conversation because missile defense is important to both of our nations," added Dempsey.

The Wall Street Journal reported earlier in the day that the US side is planning a "major expansion" of missile defense in Asia, a move said to contain threats from the Democratic People's Republic of Korea (DPRK), but the paper quoted officials as saying it could also be used to counter China's military.

China has made clear its military is defensive in nature, and called on the US side not to excite tensions in the region.

State Department Spokeswoman Victoria Nuland, when asked about the plan during her regular briefing Thursday, said missile shields are "defensive systems," and the Asia systems are designed against the threat from DPRK, and "they are not directed at China, " noting the US side has discussed with China on the system's intent through military and political channels.