The United States believes North Korea may possess a clandestine nuclear facility and could develop an additional nuclear testing site in the future.

In its latest report on arms control, nonproliferation and disarmament agreements, the State Department reiterated previous assessments that the North covered up its nuclear activity.

The report cited Pyongyang’s refusal to cooperate with the International Atomic Energy Agency(IAEA) and its failure to fully disclose information on its nuclear power generation the previous year.

The department said it remains concerned about the regime's uranium enrichment and reprocessing activities, referring to the IAEA's analysis that Pyongyang has maintained workers at its active nuclear facilities.

Washington also suspected that Pyongyang may utilize its new experimental light water reactor under construction in the Yongbyon area to secure uranium enrichment technology for nuclear materials production.

Stating that it is unclear whether the regime completely demolished its Punggye-ri nuclear testing facility in May 2018 as it has claimed, the report suggested that the North may possibly develop additional sites.