It can be ruled out. No country, not the US, not DPRK, not China, not Russia and not Iran, is going to launch any nuclear strikes at anyone else. This is not the Cuban Missile Crisis. This is the sabre-rattling of an impoverished and badly managed nation's government in order to encourage further aid from Seoul and Washington and nothing more. They do it in this manner purely because they've been at the "America is the great satan" patter for so long that they simply can't be seen to go begging to them, so they're making it look to their uneducated, starving masses like they're holding the world to ransom at the end of a big stick, when the reality is just about as far from that as possible.
There will be no war with the West and DPRK and people need to start realising that.