The USA is just setting the motion for a war against North Korea.

https://uk.news.yahoo.com/north-korea-will-destroyed-reckless-behaviour-continues-us-ambassador-warns-090000879.html

The USA already knew that sanctions won't work on NK but still insisted on sanctions because it would give the USA the excuse to wage a war against NK after all the available avenues had been exhausted.  However, it's a wishful thinking because China & Russia won't allow a war at their doorsteps.  Having a war near China & Russia means that China & Russia will have to deal with millions of refugees and also the USA influences on the Korean peninsula after the war.  This kind of situation is something China & Russia don't want to see and they'll definitely get involved in the war.