The North has pulled out of its last remaining nuclear obligation
North Korea has blamed the United States for the current nuclear crisis and vowed to boost its defences, in an unusually detailed report to coincide with a US visit by the South's president.
The latest rhetorical blast follows comments by Pyongyang that it has decided to scrap a 1992 agreement designed to keep the region free of nuclear weapons.
Speaking in New York, South Korea's President Roh Moo-hyun urged North Korea to give up its nuclear programme, saying that developing nuclear weapons would threaten stability throughout the region.
Mr Roy, who will meet President Bush in Washington on Wednesday, asked Pyongyang to come forward as what he called "a responsible member of the international community".
Speaking to the Korea Society in New York, the South Korean leader, who is on his first American visit since taking office in February, said that the North had two alternatives before it.
"It can go down a blind alley
or it can open up," said Mr Roh.
It is President Roh's first visit to the United States
Pyongyang on Monday described a 1992 agreement with Seoul to keep the Korean peninsula nuclear-free as a "dead document", nullified because of America's hostile policy towards the North.
It was the last of North Korea's legal obligations to keep itself free of nuclear weapons, after it pulled out of the global nuclear arms control treaty, the NPT, earlier this year.
North Korea continued its rhetorical offensive on Tuesday, saying that it would boost its defences "to destroy aggressors at a single stroke".
Pyongyang's latest comments appear to be carefully timed to exploit differences between Seoul and Washington, our correspondent says.
Washington has not ruled out a military option to force North Korea to back down on the nuclear issue, and hardliners are pushing for sanctions.
But South Korea opposes the use of force, and favours continued engagement with the Communist state.
Washington is also deeply concerned about North Korea's suspected missile trading.
North Korea allegedly exported $580m worth of ballistic missiles to the Middle East in 2001, according to a US military officer in Seoul quoted by the Associated Press on Tuesday.
Pyongyang also exports millions of dollars-worth of narcotics and counterfeit US money, the official said, citing "open source documents".
In December, a shipment of North Korean missiles bound for Yemen was briefly stopped in the Arabian Sea.
And last month, a North Korean ship was discovered off the coast of Australia, containing 50 kg (110 pounds) of heroin, worth US$48 million.
While North Korea has denied involvement in drug trafficking, it has often said it has the right to export missiles.