John Everard is a former British ambassador to North Korea. The opinions in this article belong solely to the author.

North Korea has probably not yet mastered two key technologies -- how to miniaturize a warhead (small bombs are more difficult than big ones) and how to get a missile back through the atmosphere without it spinning out of control or burning up. But with a missile of this range, North Korea is dangerously close to being able to credibly threaten a nuclear strike on an American city.

How can this be stopped?

The North Korean leadership seems to believe that its nuclear and missile programs are vital to its survival. It is convinced (is it wrong?) that when it can credibly threaten to obliterate an American city, Washington will no longer dare to seek its overthrow, nor will the US attempt to reinforce its South Korean ally, should North Korea attempt to reunify the peninsula by force.

It has stated clearly and repeatedly that its nuclear and missile programs are not bargaining chips to be negotiated away. And it has ridden out sanctions, even tough ones, rather than give up the programs

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