"We declare solemnly and confidently that the foolish politicians around the world, including the puppet group in South Korea, should not expect any change from us," state media said in a statement attributed to the National Defense Commission.

It also said that the country would never deal with South Korean President Lee Myung-bak, who has linked aid to denuclearization.

Six-party talks on North Korea’s nuclear program - involving the two Koreas, China, the U.S., Russia and Japan – are currently stalled.

The isolated east Asian state has seen two days of mourning for Kim Jong-il, who had ruled North Korea since 1994. He died on 17 December of a heart attack, state media said.

His son, Kim Jong-un, has since been named "supreme leader of the party, state and army.” Little is known about Kim Jong-un, except that he is in his late twenties and has had some schooling in Switzerland.