They better be afraid of it. Somehow I don't believe this is a time for taunting the U.S.
This is political posturing that seeks to provoke the US into war and to claim victimhood because of the US. In fact it follows Saddam's rhetoric of hiding nukes and leaking information of possession of nukes, so that the US be tempted to attack without a clear proof of whether there is a real threat there.
Evil always seeks to preserve not to destroy. North Korea would not wage a war but seek to isolate the US. It partialy successfuly did that when South Korea's liberal Kim stunningly criticized the US for not funding North Korea. This is as if Israel said that America is to blame because it does not give enough funds to the PA, making them starve and short changing them. It's an astounding reversal of political clout for the US in Korea - because of the Clintonist traitor in the South who is seeking or got his peace prize.