North Korea issued a New Year's message on Monday calling for great efforts for strengthening defense capabilities as it celebrates its possession of nuclear weapons. North Korea's "nuclear deterrent serves as a powerful force for defending peace and security in Northeast Asia and guaranteeing the victorious advance of the cause of independence," said a joint editorial carried by North Korea's Rodong Sinmun and two other major state-run newspapers. North Korea traditionally marks New Year's Day with a joint editorial by the country's three major newspapers representing its communist party, military and youth militia force. "All soldiers must mercilessly defeat any invasion of the US imperialists," said editorial, calling for efforts to make the whole communist country an impregnable fortress.