John Schilling, an aerospace engineer with expertise in the North's missile programs, said that the North's ICBM test could involve a missile variant of the space launch vehicle Unha or the road-mobile KN-08 missile or its upgraded version KN-14.

A test of the Unha rocket fitted with a reentry vehicle large enough for a nuclear warhead would likely work, but it would put “an end to any pretense or hope of a peaceful space program,” the expert said.

The North has twice succeeded in putting a satellite into orbit on the Unha rocket, first in late 2012 and second in February last year. Pyongyang claimed the launches were for peaceful space development purposes, despite widespread criticism it's for testing missile technology.

“If the North Koreans really want to impress anyone, and particularly if they have any hope of their space program being seen as a peaceful endeavor that might escape the political and economic sanctions imposed on North Korea's missile programs, they will want to demonstrate their ICBM capability using a KN-08 or KN-14 mobile missile,” Schilling said.

“In any case, the first test of an entirely new multistage missile whose main engine has only recently been demonstrated on the ground will almost certainly end in failure,” he said, referring to the two road-mobile ICBMs.

Still, even a failure might put the North on a path to success, he said.

Schilling also noted the first American ICBM, the SM-65 Atlas, failed 26 seconds into its maiden flight and eight tests were conducted over the course of a year, with only two fully successful. The first all-up test of the competing SM-68 Titan was even shorter, exploding on the launch pad, he said.

“We should expect North Korean ICBMs to follow a similar path -- a series of early failures leading to an operational capability even with a spotty testing record,” the expert said.

The North is unlikely to conduct an ICBM test as frequently as it did with the intermediate-range Musudan missile that was tested eight times between April and October last year, he said.

“Pyongyang can afford to keep up that pace in a full-scale ICBM development program. Its aerospace industry hasn't demonstrated the production capacity needed to test an ICBM every month,” he said. “

One test every three to six months would be more realistic, at least in the long run, so this is not a process that will be completed in 2017.”

Should the North decide to test the KN-08 or KN-14, it is expected to use existing launch sites, rather than a mobile launcher, in order to reduce chances of failure and to learn as much as possible from the failures, he said.