US President Donald Trump has announced sanctions on North Korea that open the door wider to blacklisting people and entities doing business with the rogue nation, including its shipping and trade networks, further tightening the screws on Pyongyang's nuclear and missile program.

In New York on Thursday, local time, Trump also said that Chinese President Xi Jinping had ordered Chinese banks to stop conducting business with Kim Jong Un's regime, a crucial step by North Korea's largest trading partner.

Trump praised Xi, calling it a "very bold move" in acting to cut off financial ties with North Korea and said it was "somewhat unexpected".

Pyongyang has resisted mounting international pressure, conducting its sixth and largest nuclear test on September 3, and launching numerous missiles this year, including two intercontinental ballistic missiles and two other rockets that flew over Japan.