Speaking at the World Economic Forum in Davos, Mr Powell said Washington was prepared to talk to Pyongyang about the nuclear issue.

CRISIS CHRONOLOGY

16 Oct: N Korea acknowledges secret nuclear programme, US says 14 Nov: Oil shipments to N Korea halted 22 Dec: N Korea removes monitoring devices at Yongbyon nuclear plant 31 Dec: UN nuclear inspectors forced to leave North Korea 10 Jan: N Korea pulls out of anti-nuclear treaty 11 Jan: Pyongyang suggests it could resume ballistic missile tests 24 Jan: North-South talks end without making progress

Timeline of tensions

But the talks should focus on how North Korea "will meet its obligations to completely dismantle its nuclear weapons programmes," he insisted.

North Korea has called for direct talks with the US, indicating that it opposes moves to internationalise the nuclear issue.

But on Sunday the North's official Rodong Sinmun newspaper called for "national co-operation" with South Korea.

Seoul is to send two special envoys to Pyongyang aboard a presidential plane on Monday to discuss the crisis and inter-Korean exchanges.

Mr Powell said the United States "has no intention of attacking North Korea... At the same time we are keeping all our options on the table."

Now that the US imperialists' hostile moves against (North Korea) have reached the extremes, national co-operation is the way of saving the nation and the way of patriotism North Korea's Rodong Sinmun newspaper

"We are prepared to convey this in a way that makes it unmistakeable to North Korea," he said.

North Korea is demanding a non-aggression pact with the United States.

Washington has ruled out a formal treaty but has hinted that it might provide a written security guarantee.

Mr Powell stressed that Washington was ready to "build a different kind of relationship" with North Korea once Pyongyang complied with its commitments and showed willingness to "act in a manner that builds trust".

The US would continue to contribute to North Korea's humanitarian needs, he said.

IAEA meeting

South Korea has urged the United Nations nuclear watchdog to postpone an emergency meeting on the North Korean crisis, asking for more time to allow diplomatic efforts to work.

The International Atomic Energy Agency (IAEA) has said it will hold an emergency session on 3 February to decide whether to refer the matter to the UN Security Council.

A special envoy of South Korea's outgoing President, Kim Dae-jung, and an envoy from President-elect Roh Moo-hyun are set to travel to Pyongyang on Monday.