Following North Korea's new high-thrust rocket engine test on Sunday, it's widely believed the North has mastered many core technologies, including rocket engine propulsion and missile separation.
"North Korea appears to have tested one main and four sub-engines that are connected to make a new rocket engine. We believe North Korea has made some progress in terms of its engine capabilities."
However, military experts believe Pyongyang has not yet secured the most complex step: missile re-entry technology.
Such technology allows an ICBM to successfully reenter the earth's atmosphere with no damage to the warhead.
An ICBM with a range of one thousand kilometers re-enters the atmosphere at a average speed of 24 MACH -- or some 30-thousand kilometers an hour -- and the warhead has to endure temperatures of more than seven thousand degrees Celsius.
While this hole in the North's technical ability buys the U.S. and its allies some time, experts agree the regime will eventually acquire the re-entry technology and have a deliverable ICBM within five years.
Once the technology is mastered, a North Korean ICBM could target the west coast of the mainland United States.
U.S. officials have said that, as Pyongyang gets closer to having a deliverable nuclear weapon, Washington should be ready to take pre-emptive measures.
North Korea has conducted six ICBM tests since 1998, accumulating a high degree of knowhow and technology over the years.
Kim Hyun-bin, Arirang News.