Kim Yong-Chun, chief of the general staff of the North Korean People's Army, warned the United States that it would face any aggression head on.

"The army and the people of the DPRK (North Korea) will never remain a passive onlooker to the US moves to isolate and stifle the DPRK, but steadily bolster its nuclear deterrent for self-defence to cope with the enemies' reckless moves for military aggression," he said in a speech carried by the official Korean Central News Agency.

"Should the US start a war..., the revolutionary armed forces of the DPRK will mobilise the military deterrent force built up for years and... win a final victory in the stand-off with the US."

The remarks, made in a speech marking the 73rd anniversary of the North's military, came as Washington was hardening its position towards Pyongyang for boycotting six-way nuclear disarmament negotiations.

US Secretary of State Condol-eezza Rice warned Thursday of referring the issue to the UN Security Council for possible sanctions on North Korea in case the talks failed to deliver.

The talks, which involve the two Koreas, China, Russia, the United States and Japan, have stalled since three rounds ended inconclusively in June, 2004.

The North failed to show up for a fourth round scheduled for September 2004.

The Stalinist state declared in February that it had built nuclear weapons to use in self-defence against the United States.