"North Korea probably has missiles under development that we don't know about, but the likelihood of any such missile being ready for an imminent flight test without our first having seen signs of extensive ground testing is very low," he said in an article carried by the website 38 North.

"One possibility is that we are not seeing a complete missile: N-14 mobile intercontinental ballistic without the re-entry vehicle or a KN-08 mobile ICBM without the third stage, would meet the description provided," he said. 

It would be unusual to mount the missile on a mobile launcher in an incomplete configuration, but it might be done if the re-entry vehicle is stored separately and the mobile launcher is the most expedient way to deliver the missile to the launch site, the expert said. 

"If this is the case, we might expect a demonstration launch in the next few days," he said.

Another possibility is that the North might launch a KN-08 with only the first two stages if the third stage is facing severe technical difficulties, he said, though the case seems unlikely because both the guidance system and the attachment fitting for the re-entry vehicle are part of the third stage.

The North could launch a missile with a dummy third stage containing only the guidance and payload systems, with the ballast in place of the engines and fuel, Schilling said, adding that there is precedent for this in other countries' large rocket testing, but the rocket would still be of normal length.

"They may launch a KN-08 or KN-14 missile after adding a yet-unseen re-entry vehicle (and in the case of a KN-08, the entire third stage). Such a test would probably fail and embarrass the regime, but it could fail in a way that provides Pyongyang's engineers with critical data going forward," Schilling said. 

"North Korea usually fails with their first test of a new missile and usually figures out how to make it work in the end," he said.

A final possibility is that the missile is a plain old-fashioned Nodong missile, the workhorse of North Korea's strategic arsenal and just about 15 meters long, the expert said. 

North Korean leader "Kim Jong-un's engineers almost certainly understand that any test of a new ICBM rushed to meet a political deadline will likely result in failure, and if they have had the courage to tell their boss this, then Kim might settle for posturing with shorter-range missiles," he said. (Yonhap)