The U.S. State Department reportedly shares the International Atomic Energy Agency's grave concerns over North Korea's nuclear activities.
This according to a source who spoke to Voice of America on Friday.
The source added that verification of any denuclearization agreement with the North will be difficult and a process that will have to involve the IAEA.
The UN's nuclear watchdog said this week that it has reason to believe North Korea is still operating its main nuclear site in Yeongbyeon.
The head of the IAEA also called on North Korea to allow international inspectors into the regime so they can independently verify Pyeongyang's nuclear activities.