"Given their past behaviour, given the belligerent manner in which they are constantly threatening their neighbours, I don't think there's any question that that would be a destabilising situation that would be a profound threat to not only the United States' security but to world security," Obama said at a joint press conference with the visiting South Korean President Lee Myung-bak.
Obama said North Korea also has a track record of proliferation that makes it unacceptable for them to be accepted as a nuclear power. They have not shown, in the past, any restraint in terms of exporting weapons to not only state actors but also non-state actors, he said.
"So what we have said is that there is a path for North Korea to take in which they are joining the world community, becoming integrated into the world economy, able to feed their own people, able to provide prosperity for their people," Obama said.
President Lee of South Korea said the North Koreans must understand that their past behaviour will not stand. "Not only will the US-Korea close partnership, but Japan, China and the rest of the international community takes part in this effort. Now the North Koreans will come to understand that this is different, that they will not be able to repeat the past or their past tactics and strategies," he said.
Urging the North Koreans to fully give up their nuclear weapons program and ambitions, Lee said the Pyongyang regime needs to become a responsible member of the international community.
Earlier, alleging that North Korea has abandoned its own commitments and violated international law, Obama said its nuclear- and ballistic-missile programs pose a grave threat to peace and security of Asia and to the world.
Reiterating shared commitment to the complete denuclearization of the Korean Peninsula along with President Lee, Obama reaffirmed the endurance of their alliance and America's commitment to the defence of South Korea.
"We discussed the measures that we are taking with our partners in the region, including Russia, China and Japan, to make it clear to North Korea that it will not find security or respect through threats and illegal weapons," he said.
Referring to the resolutions adopted by the United Nations Security Council, he said, "Now we must pursue a sustained and robust effort to implement this resolution together with our international partners."
