SEOUL, Jan. 19 (Xinhua) -- The Democratic People's Republic of Korea (DPRK) can test-launch an intercontinental ballistic missile (ICBM) at any time when its leadership decides, South Korea's military said Thursday.

A Joint Chiefs of Staff (JCS) official told a regular defense ministry briefing that under such assessment, the South Korean military is maintaining defense readiness.

Armed forces of South Korea and the United States are cooperating in preparations for the DPRK's ICBM threats, jointly operating surveillance assets and closely monitoring relevant moves, the official said.

Top DPRK leader Kim Jong Un said in his new year speech that his country had entered a final stage to prepare for the test-fire of a long-range ballistic rocket, indicating the ICBM test-launch in the foreseeable future.

Yonhap news agency cited sources of South Korea and the United States as saying that Pyongyang had produced a new type of two ICBMs that are already mounted on mobile launchers. It would be very hard to detect missiles fired from mobile launchers.

According to the sources, the new long-range missiles are less than 15 meters in length, shorter than the 19-20 meter KN-08. Its enhanced version, KN-14, is 17-18 meters in length.