GENEVA (Reuters) - North Korea accused the United States on Wednesday of contributing to an "unpredictable" situation on the divided Korean peninsula and abusing its power in the U.N. Security Council to impose its "hostile policy" against Pyongyang.

North Korea is facing further U.N. sanctions for its underground nuclear test explosion two weeks ago, its biggest and most powerful to date which prompted warnings from Washington. In December it launched a long-range rocket.

"The U.S. is to blame for the situation on the Korean peninsula which is inching close to an unpredictable phase now," So Se Pyong, North Korea's ambassador to the U.N. in Geneva, told the U.N.-sponsored Conference on Disarmament.

"The U.S. should no longer be allowed to seriously infringe upon the independent right of the DPRK to use space for peaceful purposes nor should it be allowed to abuse the U.N. Security Council as a tool for executing its hostile policy toward the DPRK," he added, using the acronym for the Democratic People's Republic of Korea.

"The third nuclear test was carried out as part of the practical countermeasures for defending the country's sovereignty and security to cope with ruthless hostile behaviors of the U.S., which wantonly infringed upon the DPRK's legitimate right to satellite launch for peaceful purposes," So said.

Earlier, Ireland's foreign minister Eamon Gilmore, in a speech to the Geneva forum, called on North Korea to cease immediately nuclear testing and ballistic missile activities and re-engage in stalled six-party talks on denuclearization.

(Reporting by Stephanie Nebehay; Editing by Jon Hemming)