North Korea's envoy to the United Nations says his country will not return to the six-way nuclear talks unless the United States offers an apology for calling the North an "outpost of tyranny."

Deputy Ambassador to the U.N. Han Song-ryol made the remarks Thursday during a telephone interview with Seoul-based Yonhap News Agency.

His remarks came shortly after the North's Foreign Ministry announced that Pyongyang wants the six-party nuclear discussions to be upgraded into comprehensive disarmament talks.

Han repeated his government's position that it will return to the six-party talks if certain conditions are met, including Washington's apology for labeling Pyongyang an "outpost of tyranny."

Han said U.S. Secretary of State Condoleezza Rice's referral to the North as a "sovereign state" during her Asian tour last month could not be interpreted as an apology.

Asked about the possibility of Pyongyang's nuclear issue being referred to the U.N. Security Council if it continues to boycott the nuclear discussions, Han said his country would regard such a move as a declaration of war.