Critics say the North is trying to win concessions from Seoul and improve its image in the face of increasing international sanctions over its nuclear and ballistic missile programs.

Asked about the meeting, Pentagon spokesperson Lt. Col. Chris Logan told Yonhap the defense chiefs will discuss "matters of mutual concern."

"We won't get into the specifics of their conversation until after the meeting," he added.

Seoul's defense ministry said the meeting will be a chance for the allies to share views about security situations on the Korean Peninsula and discuss diverse issues including their cooperation to make the upcoming PyeongChang Winter Olympics a peaceful and safe event.

Seoul and Washington have postponed their annual military exercises to ensure Pyongyang does not conduct nuclear or missile provocations around the Olympics. North Korea views the drills as an invasion rehearsal.

Mattis reiterated the US will not accept North Korea as a nuclear power.

"It is the public and stated policy of the United States, of Republic of Korea, of Chinese, of Russian Federation, and I can go on, that the Korean Peninsula, due to its unique circumstance, the fact that there's been no peace treaty, just an armistice, this is not a place where the international community can tolerate nuclear weapons," he said, referring to the 1950-53 Korean War that ended in a truce, leaving the Koreas technically at war. (Yonhap)