Isolationist North Korea lashed out at its neighbour on Wednesday for hosting an international nuclear security summit in Seoul next month, calling it a childish farce and an intolerable grave provocation.
The South has said Pyongyang can send a delegate to the conference involving some 50 world leaders, including U.S. President Barack Obama, but insists the invitation is conditional on it renouncing its own nuclear programme.
The two Koreas are still technically at war, having signed only a truce to end their 1950-53 civil conflict, not a peace treaty, and the United States has some 28,000 troops based in the South.
It is astonishing that a meeting dealing with the issue of nuclear security is to be convened in south Korea, a nuclear advance base for the U.S. and the world's largest nuclear powder magazine, KCNA state news agency quoted an official statement as saying.
Referring to south Korea without the capital S is its way of denying its existence as a separate country. It said the March 26-27 summit showed that south Korea was a special-class nuclear war servant for its American master.
The United States guarantees the South's security under its so-called nuclear umbrella, but says it does not keep nuclear weapons on the peninsula.
The North itself has twice tested nuclear devices, and analysts say it has enough fissile material to make more half a dozen atomic bombs.
Pyongyang, subject to international sanctions for its nuclear weapons programme, has said it is willing to rejoin regional talks which offer the impoverished state aid in return for giving up its nuclear weapons programme.
Experts, however, doubt the North's new leadership has any intention of giving up its pursuit of nuclear weapons because it sees them as a deterrent against attack and a negotiating chip.
North Korea and U.S. officials will meet in Beijing on Thursday for a third round of bilateral talks aimed restarting the regional six-party nuclear talks which broke down in 2009.
Glyn Davies, who will lead the talks for the U.S. side, said North Korea needed to show it was sincere, but that he was pleased the talks were happening so soon after the death of Kim Jong-il and appointment of his son Kim Jong-un as leader.
What precisely his policies are, in what direction he wants to take his country -- all of these are a bit unknown at this stage, he told reporters in Beijing.
The Seoul nuclear security summit is focused on preventing nuclear terrorism and safeguarding nuclear materials and facilities.
(Reporting by Jeremy Laurence; Additional reporting by Ben Blanchard in Beijing; Editing by Sanjeev Miglani)