U.S. Secretary of State Hillary Clinton has created ripples by saying North Korea owns up to six nuclear weapons.

Clinton made the remark at a nuclear non-proliferation lecture at University of Louisville in Kentucky. She said even as she was speaking, there were countries seeking nuclear weapons.

The comment goes a step further than her remarks in late March that North Korea has a nuclear weapon, unlike Iran, which did not at the time.

The State Department's Special Advisor for Nonproliferation and Arms Control Robert Einhorn commented on Friday Korean time that North Korea owns a nuclear weapon, in line with Clinton’s remark. Einhorn has led preparations of the Nuclear Posture Review Report.

The U.S. government has until now strenuously denied that North Korea has a nuclear weapon, although it acknowledged the North had the capability.