President Donald Trump has announced a new order to help the US target people, companies and banks financing and facilitating trade with North Korea.
He also praised China for reportedly ordering banks to stop doing business with Pyongyang.
Mr Trump's actions follow his speech at the UN General Assembly this week, when he escalated his rhetoric against North Korea amid a months-long crisis over Kim Jong-un's expanded missile testing programme.
He spoke of his own nation's "patience", but said that if "forced to defend itself or its allies, we will have no choice but to totally destroy North Korea".
Mr Trump said his new executive order would disrupt other trade avenues for North Korea in efforts to halt its nuclear weapons programme.
The new order enables the US to sanction individual companies and institutions that finance trade with North Korea.
He made the announcement on Thursday during a working lunch with Japanese Prime Minister Shinzo Abe and South Korean President Moon Jae-in.
Mr Trump said "tolerance for this disgraceful practice must end now".
He also saluted China's central bank for what he said was a move to stop its banks from trading with North Korea. That development was reported by Reuters on Thursday.