U.S. Treasury Secretary Steven Mnuchin said that banks doing business in North Korea would not be allowed to operate in the US under a new sanctions order. Picture: AP Photo/Carolyn Kaster, File

New York - U.S. Treasury Secretary Steven Mnuchin said on Thursday that banks doing business in North Korea would not be allowed to also operate in the United States under a new sanctions order aimed at thwarting Pyongyang's nuclear and missiles programme.

"No bank in any country should be used to facilitate Kim Jong Un's destructive behavior," Mnuchin told reporters, referring to North Korea's leader. "Foreign financial institutions are now on notice that going forward they can choose to do business with the United States or with North Korea, but not both."

Mnuchin said any sanctions issued under the new executive order signed by U.S. President Donald Trump on Thursday would be forward-looking and not target past behavior.