It is unclear how Campbell, who is known to be well-versed in Japanese affairs, has responded but the source told Kyodo News that he will accept the offer.

A State Department official said that if Campbell assumes the post, it would be favorable to Japan as he could serve as a counterweight to Clinton, who some in Japan fear would lead the United States to tilt toward China.

Campbell served as deputy assistant secretary of defense for Asia and Pacific affairs under the administration of former President Bill Clinton. In that capacity, he played a central role in redefining the Japan-U.S. alliance, including a review of the guidelines for bilateral defense cooperation.

Campbell would replace Christopher Hill, who has been the chief U.S. delegate to the six-party talks on ending North Korea's nuclear drive. But the official said the transition team of President-elect Barack Obama plans to create a new post, such as coordinator or special envoy, to handle North Korean issues.

As a result, Campbell would probably not be greatly involved in the six-way negotiations but would rather focus on bilateral relations with countries such as Japan, China, South Korea, Taiwan and Myanmar.

Who will be in charge of North Korean issues has yet to be determined, but there is speculation that Hill could continue as the U.S. point man.

Campbell is currently chief executive officer of the Center for a New American Security, a Washington think tank. He is also a member of the advisory board of the Center for Strategic & International Studies, another Washington think tank.