United Nations Secretary-General Ban Ki-moon attends a press conference at the UN headquarters in New York, on April 17, 2013. Ban on Wednesday called the Korean Peninsula crisis " highly volatile" and urged the Democratic People's Republic of Korea (DPRK) to return to the negotiating table. (Xinhua/Niu Xiaolei)

United Nations Secretary-General Ban Ki-moon (C) attends a press conference at the UN headquarters in New York, on April 17, 2013. Ban on Wednesday called the Korean Peninsula crisis " highly volatile" and urged the Democratic People's Republic of Korea (DPRK) to return to the negotiating table. (Xinhua/Niu Xiaolei)

United Nations Secretary-General Ban Ki-moon attends a press conference at the UN headquarters in New York, on April 17, 2013. Ban on Wednesday called the Korean Peninsula crisis " highly volatile" and urged the Democratic People's Republic of Korea (DPRK) to return to the negotiating table. (Xinhua/Niu Xiaolei)

United Nations Secretary-General Ban Ki-moon (C) attends a press conference at the UN headquarters in New York, on April 17, 2013. Ban on Wednesday called the Korean Peninsula crisis " highly volatile" and urged the Democratic People's Republic of Korea (DPRK) to return to the negotiating table. (Xinhua/Niu Xiaolei)

United Nations Secretary-General Ban Ki-moon (L) attends a press conference at the UN headquarters in New York, on April 17, 2013. Ban on Wednesday called the Korean Peninsula crisis " highly volatile" and urged the Democratic People's Republic of Korea (DPRK) to return to the negotiating table. (Xinhua/Niu Xiaolei)