U.S. Secretary of State Rex Tillerson has appealed to the international community, especially Russia and China, to stop the spread of nuclear weapons. He says North Korea is a case study of the failure to prevent rogue states from obtaining weapons of mass destruction.

Tillerson recalled that Washington and Moscow co-operated during the Soviet era, despite their Cold War rivalry, on measures to stop weapons proliferation. And he said, "We should do so again."

Tillerson spoke Thursday at a ministerial meeting of the U.N. Security Council called by the United States on "the acute threat" posed by the proliferation of nuclear, chemical and biological weapons. It cited three countries in a note to council members that have been targeted by council resolutions - North Korea, Iran and Syria.