Mark Lippert, Defense Secretary Chuck Hagel's chief of staff, will lead the U.S. delegation to an upcoming trilateral defense meeting with South Korea and Japan, informed sources here said Monday, as he is considered a strong candidate to become Washington's new ambassador to Seoul.

The assignment apparently reflects Lippert's direct influence over Korea and other regional affairs, a year after leaving the post of assistant secretary of defense for Asian and Pacific issues.

David Shear, a diplomat nominated to succeed Lippert, has not started his work at the Pentagon yet.

Lippert will participate in the two-day Defense Trilateral Talks (DTT) to open in Washington, D.C., on April 17, according to sources.

It's highly unusual for Lippert to head the U.S. team, given his current position.

"It's because he is well aware of issues to be discussed at the meeting, especially North Korea," a source told Yonhap News Agency.

South Korea will likely be represented by Deputy Defense Minister Ryu Je-seung and Japan's delegation will be led by a director general-level official.

Another source said Lippert has continued to play a key role in the Obama administration's defense policy in Asia amid its push for rebalancing toward the region.

He is now traveling to China with Hagel.

In particular, Obama may pick him as his new ambassador to South Korea.

The current envoy, Sung Kim, reportedly plans to finish his work in Seoul as early as September after a three-year stint.

His successor needs to be decided in the coming months, given the time necessary for Senate confirmation.

"For now, there is no specific name we are hearing other than Mr. Lippert on Kim's possible successor," a diplomatic source told Yonhap.

If he is chosen, he would become the first non-career diplomat to become Washington's top envoy in Seoul.

Lippert seems to want the job, hoping to get a new post before too late, and South Korea would also support that as he has direct connection with Obama, according to the source. Lippert is a longtime key aide to the president.

South Koreans closely watched Obama's selection of Caroline Kennedy as ambassador to Tokyo and senior Sen. Max Baucus as ambassador to Beijing, the source pointed out. (Yonhap)