The Pentagon is searching for a new key policymaker on Asia, as Peter Lavoy, acting assistant secretary of defense for Asian and Pacific Security Affairs, will step down from the post next month, a source said Wednesday.

Lavoy is leaving the Pentagon in the first or second week of January after more than two years of service at the department amid the Obama administration's stated policy of rebalancing toward the Asia-Pacific region, according to the source.

It remains uncertain when a new assistant secretary of defense for Asian and Pacific affairs will be nominated.

"The job may go to an outside figure or a military officer with lots of experience in Asia," the source told Yonhap News AGency on the condition of anonymity.

David Helvey, deputy assistant secretary of defense for East Asia, is expected to stay in office for working-level affairs on Korea, Japan and China, added the source.

Lavoy joined the Department of Defense in August 2011 as principal deputy assistant secretary for Asian and Pacific Security Affairs. He has worked as acting assistant secretary since Mark Lippert left the position early this year to take up the post of chief of staff to Secretary of Defense Chuck Hagel.

Lavoy's upcoming departure is part of the ongoing reshuffle of top Pentagon officials.

James Miller, under secretary of defense for policy, is also resigning in January.

Rear Adm. John Kirby, the Pentagon's new press secretary, began his official duties this week. (Yonhap News)