Ruggiero, currently a senior fellow at the Foundation for Defense of Democracies, called for sanctioning more Chinese banks to cut off revenue streams to the North Korean regime.

"It is surprising that people want to claim that 10 months of robust sanctions have failed, when really 10 years of not only failed policies but a failed sanctions approach failed," he said. "So I think we have to be very careful about what we look at and suggesting that the time has come to move beyond North Korea sanctions."

US President Donald Trump threatened last week to impose more sanctions on Pyongyang after it launched a new intercontinental ballistic missile apparently capable of striking all parts of the United States.

Asked about the plan, White House press secretary Sarah Sanders said it is in the works.

"We expect the Department of Treasury to put out more details on that, hopefully by the end of this week," she told a regular news briefing. (Yonhap)