National Security Adviser Wi Sung-lac said Friday that North Korea's recent unveiling of the hull of what it calls a nuclear submarine has posed a new threat to South Korea, while taking a cautious tone on the capabilities of the North's submarine. Last week, North Korea's state media released undated images of the completed hull of an 8,700-ton nuclear submarine, with leader Kim Jong-un inspecting it. When asked about the North's unveiling of the hull of a nuclear submarine, Wi replied that, "As a new type of threat for us, it needs to be dealt with." Still, Wi said there has been little information about the capabilities of the North's nuclear submarine, describing such information as an "area that needs to be further figured out." President Lee Jae Myung is set to visit China next week for summit talks with Chinese President Xi Jinping, with North Korea expected to be one of the main agenda items. Wi stressed that South Korea's plan to build a nuclear-powered submarine would not violate the Nuclear Non-Proliferation Treaty (NPT) or International Atomic Energy Agency (IAEA) guidelines,