You are incorrect Bill, that threat you mention was an old reference to artillery and not nuclear weapons.
In fact when that threat was made NK was vigorously denying their possession of nuclear weapons.
http://www.cbsnews.com/stories/2003/01/12/world/main536171.shtml wrote:(CBS) North Korea denied Sunday ever admitting to U.S. officials that it had a secret nuclear weapons program and said it would unleash a "sea of fire" if the United States challenges the communist country.
Conservative blogs often conflate this threat with the later discovery of a nuclearized pennensula but they do this in error.
And as to the US threat we are a diplomatically advanced nation and will very rarely commit a "we will nuke you" gaffe.
What we did do is move nukes onto the pennensula and we leaked contingency plans for pre-emptive nuclear strikes.
We also publically discussed developing "bunker-buster" nukes to use in a pre-emptive strike on North Korea's arsenal.