The bill also cracks down on North Korean shipping and use of international ports and requires the administration to determine whether North Korea is a state sponsor of terrorism.

The Senate must pass the legislation before it becomes law.

Calls for tougher sanctions on the North have risen again after American college student Otto Warmbier died just days after he was released from North Korea in a coma following 17 months of detention for taking down a political propaganda sign from a hotel.

"It's time for the Senate to act on Chairman Royce's bill. Doing so will give the United States powerful new tools to address North Korean threats," the office said in a release.

The office said there are "myths" about sanctions on the North, such as a belief that the North is the most sanctioned country in the world, but those perceptions are not true and there is plenty of room for more sanctions.

"Serious pressure on North Korea has been applied unevenly, only to be lifted prematurely for promises that never materialized," the office said. "North Korea may not even be in the top five most-sanctioned countries, with Iran, Syria, Burma, Zimbabwe and Belarus facing tougher sanctions."

The office also cited as an example the 2005 US blacklisting of a Macau bank for doing business with Pyongyang. The designation scared away other financial institutions from dealing with Pyongyang for fear they would also be blacklisted.

But the sanctions were "lifted prematurely for more empty promises from the regime," the office said. "There is plenty of room to ratchet up pressure on Kim Jong-un and North Korea's ruling class." (Yonhap)