The United States has expressed "significant concerns" about North Korea's nuclear weapons program and pledged to keep sanctions on the country until full denuclearization is achieved. 

In its annual report on U.S. and other nations' compliance with various arms control and nonproliferation agreements, the U.S. State Department said that throughout 2019, the country continued to have significant concerns regarding North Korea's nuclear weapons program and its continued production of fissile material.

The department also raised the possibility that North Korea may have additional unidentified nuclear facilities, mentioning a report by the International Atomic Energy Agency(IAEA). 

In the report in August 2019, the IAEA said there were indications of ongoing mining activities at locations previously declared the Pyongsan uranium mine and Pyongsan uranium concentration plant.

The department said the U.S. continues to work with the international community until the goal of final, fully verified denuclearization of North Korea is achieved. It added that UN and U.S. sanctions will remain in place and will be fully enforced.