The isolated Communist country also pledged to end all efforts to denuclearize the Korean Peninsula.
The North Korean response came immediately after the 15-member U.N. Security Council unanimously approved a resolution to tighten and expand sanctions against the country after it went ahead with its Dec. 12 long-range rocket launch in violation of existing U.N. sanctions.
A North Korea Foreign Ministry statement, carried by the official Korean Central News Agency and reported by South Korea's Yonhap News Agency, blamed the United States' "worsening policy of hostility" toward North Korea and said the six-party talks on the North's denuclearization, which began in 2005, "were rendered null and the denuclearization of the Korean Peninsula was put to an end."
"There will be no more discussion over denuclearization of the Korean Peninsula in the future although there will be talks for securing peace and security in the peninsula," the ministry said.
China's official Xinhua News Agency said North Korea also pledged to "take physical actions to strengthen self-defense military capabilities including nuclear deterrence."
The Dec. 12 rocket launch, which North Korea claimed was to put a satellite into orbit, was condemned by the United Nations as a violation of existing U.N. sanctions imposed after the country's earlier missile and two nuclear tests in 2006 and 2009. Other countries saw it as a cover to test the North's intercontinental ballistic missile capability.
The latest Resolution 2087 approved by the Security Council would also require North Korea not to use ballistic missile technology in any launch. The resolution also called for a peaceful, diplomatic and political solution to the issues and urged the renewal of the six-party talks.
The six nations in the talks are the two Koreas, China, Japan, Russia and the United States. The talks have stalled since April 2009 after North Korea walked away over U.N. criticism of its earlier rocket launch.
The North's December launch came as Kim Jong Un completed one year as the isolated country's leader. He took over after the death of his father in December 2011.
There have been reports North Korea, under its new leader, may be preparing for its third nuclear test.