The missile technology, however, is missing a crucial piece, said Kristensen: the re-entry vehicle. Any intercontinental missile designed to travel from North Korea to Alaska or Hawaii needs to leave the upper atmosphere, and that means the warhead has to have shielding for when it comes back to earth to hit its target. Without it, the warhead burns up before it reaches the ground. Bits of radioactive debris might survive, but not much else.
"You just don't see the elaborate re-entry vehicle tests," Kristensen said. And that wouldn't be a secret – there is simply no way to hide such a launch. "We've spent the last 60 years monitoring every single Russian test," he said. North Korean tests are just as visible. Even preparing for one would be obvious because of the sheer size of the industrial plant involved, to say nothing of the size of the rocket.
"If I were the North Korean leader and desperate for a weapon, I'd attach it to an aircraft," said Kristensen. "A ballistic missile is the most complicated way to develop a weapon." The North Koreans haven't announced that they have a bomber capable of carrying a nuclear bomb – which would be a much more credible threat.
None of this means that the North Koreans couldn't develop these technologies in the future, but it will probably be some time.
David Straub, associate director of Korean Studies Program at Stanford University's Freeman Spogli Institute for International Studies told Discovery News that in 2011 then-Secretary of Defense Robert Gates said the direct threat to the United States would come in about five years. That means 2016.
Between now and then the DPRK would have to test more rockets, of multiple stages, as well as re-entry vehicles.
The country at the most risk is likely South Korea. In the meantime the North Koreans have threatened South Korea with "strong physical countermeasures" if it takes part in U.N. sanctions designed to punish the North for the missile tests. North Korean missiles could certainly hit targets in South Korea or even Japan with a nuclear warhead, if they have managed to build one small enough. But both Straub and Kristensen agreed that would be against Kim Jong-un's best interest. "The regime wants to survive," said Straub.
In the end, however, the real audience for such announcements may well be inside North Korea. Standing up to the United States is a good way to make the regime look like it is defending the North Korean people against a potential threat, and distracts from problems at home such as a moribund economy and persistent shortages of food and fuel.
And they aren't likely to give up, said Straub. "North Korea been pursuing and working on nuclear programs for a long time," he said. "They've invested a lot of time, a lot of energy a lot of attention at the highest levels."