UN Secretary-General Ban Ki-moon is urging North Korea to return to the negotiating table.

The UN chief said in a news conference at UN headquarters in New York that the situation on the Korean Peninsula is very unstable and the international community has responded “in a firm but measured way” to North Korea’s nuclear test, provocations and threats.

Ban said the recent developments have strengthened the international consensus that North Korea will not be accepted as a nuclear power. He added that he will continue to urge the North Korean leadership to reverse course and return to the negotiating table.

The UN secretary-general said that he is discussing the Korean Peninsula with the leaders of South Korea, the U.S. and China.