Why not prevent the nuclear project of DPRK by force? or it can has the ability to attack USA sooner or later.

Obviously it is impossible to let DPRK give up their crazy nuclear plans only by negotiation or sanction. and if they have the ability to attack USA with nuclear in the near future it is more harder to prevent their arbitrary and it is impossible to liberate DPRK people; and to make money they will sold the nuclear weapons to terrorist; USA, Japan, Korea, China and even all over the world will be in fear of their nuclear threat.