US and Japanese officials are considering deploying a new US early-warning radar to Japan to help counter possible missile threats from North Korea, officials said Thursday.

An American X-band radar is already in place in northern Japan, at Shariki base in Tsugaru City, on the coast of Aomori prefecture.

But both governments are weighing possibly adding another radar to bolster the country's missile defenses, the US military's top officer, General Martin Dempsey, said after talks with his Japanese counterpart, General Shigeru Iwasaki.

"As you know there is already an X-band radar present there. No decisions have been taken to expand that capability," Dempsey, chairman of the US Joint Chiefs of Staff, said at the Pentagon.

"But it's certainly a topic of conversation because missile defense is important to both of our nations," the general said.

Discussions for a possible additional radar come amid concern over North Korea's efforts to develop a long-range missile as well as US worries over China's investment in anti-ship missiles.

"This is an idea under consideration. It makes sense given the threat posed by North Korea," a US official, who spoke on condition of anonymity, told AFP.

State Department spokeswoman Victoria Nuland told reporters that the United States has told China that its missile defense work was not directed at the rising Asian power.

"These are defensive systems. They don't engage unless missiles have been fired. And in the case of the Asian systems, they are designed to defend against a missile threat from North Korea. They are not directed at China," she said.

The Pentagon is looking to bolster the US military's presence in the Asia-Pacific region and missile defense systems, both sea and land-based, are a crucial part of the strategy.

The Pentagon would not comment on where the radar might be located in Japan.

"Japan is one of the United States' most significant international missile defense partners. We conduct regular alliance consultations on ways we can enhance and deepen our missile defense cooperation to address the growing threat of ballistic missiles in the region," said spokesman Lieutenant Colonel Damien Pickart in an email.

The Wall Street Journal first reported on the possible radar deployment in its Thursday edition.