The Americans are hoping to force DPRK to strike first thus justifying their war planning that is already underway. You guys should really study the invasion of Iraq and the Japanese Pearl Harbour decision to better understand what is happening here.
Most likely, assuming the DPRK doesn't do anything stupid tomorrow, the US will continue to refine its war plan for another six to 12 months, then likely invent a justification for a strike, anything will do, a missile launch, perceived "aggression". Note that Trump was retweeting reports about cruise missiles being loaded onto patrol craft in DPRK, which has historical precedence in the Gulf of Tonkin incident...
In his interview with H. R. McMaster, Hugh Hewitt straight up asks the national security advisor if this is all preparation for a first strike. Check it out.