"The maritime industry must do more to stop North Korea's illicit shipping practices," national security adviser John Bolton tweeted after the Treasury Department's announcement.

"Everyone should take notice and review their own activities to ensure they are not involved in North Korea's sanctions evasion," he said.

The Treasury Department said it was blocking all potential US interests of the Dalian Haibo International Freight Co. Ltd. and prohibiting Americans from dealing with the firm.

The United States charged that the company last year shipped cargo from the Chinese port of Dalian to North Korea on behalf of the Paeksol Trading Corporation, which in the past has sold metal and coal to earn money for Pyongyang.

The Treasury Department also sanctioned the Liaoning Danxing International Forwarding Co. Ltd., saying it had assisted North Korean officials based in Europe in procuring goods for the regime.

The action comes less than a month after North Korean leader Kim Jong Un met in Hanoi with President Donald Trump for a second summit that broke down in part over Pyongyang's demands for immediate sanctions relief.

Trump, while walking away from the talks, has been eager to reach a potentially landmark agreement on North Korea's nuclear weapons program.

Treasury Secretary Steven Mnuchin, announcing the latest measures, said that the United States remained committed to seeking a denuclearization deal with North Korea but believed fully enforcing UN-backed sanctions "is crucial to a successful outcome."