In a rapidly escalating sequence of actions, Pyongyang followed its second nuclear test on Monday by restarting its fuel reprocessing plant at Yongbyon, test-firing missiles and threatening military action, showing no sign that it is ready or willing to relinquish its status as a nuclear power. South Korea's decision to join the Proliferation Security Initiative which was initiated by the US in 2003, brought a swift response: "Our revolutionary armed forces ... will regard" South Korea's participation "in the PSI as a declaration of war ..." the North's official news agency said. "North Korea threatened military action Wednesday after South Korea joined a US-led effort to limit the trafficking of weapons of mass destruction, the official Korean Central News Agency said. "South Korea said Monday that it was joining the 6-year-old Proliferation Security Initiative (PSI) because of 'the grave threat WMD and missile proliferation is posing to global peace,' said Foreign Ministry spokesman Moon Tae-young," CNN reported. "The effort is aimed at halting shipments of weapons technology, a rare source of hard currency for North Korea, but Moon said the south would continue to uphold a shipping agreement with the North. " 'Our revolutionary armed forces ... will regard' South Korea's participation 'in the PSI as a declaration of war ...' the North's official news agency said." The Daily Telegraph said: "The threat by North Korea to launch a military attack if any of its ships are subjected to 'stop and search' under the US's anti-proliferation regime raises the possibility of a repeat of the naval skirmishes that took place off the Korean coast in 1999 and 2002. "However, analysts say that with two million soldiers massed on the peninsular, with both sides having nuclear weapons and with US security guarantees to South Korea, neither side is looking for war. "Cheong Seong-Chang of the Sejong Institute think-tank said that North Korea's statement would inevitably raise cross-border tension further and a naval clash is highly possible off the west coast." RIA Novosti reported: "Russia's foreign minister said on Wednesday that the United Nations Security Council must take action to prevent North Korea from further nuclear activities, but should seek dialogue and avoid futile punishments. "The Security Council held closed-door consultations on Tuesday, the day after North Korea's underground nuclear test explosion. Russia has called for a 'strong resolution' against Pyongyang, while other countries have proposed sanctions. " 'The Security Council must speak out firmly and outline measures to prevent a further erosion of the non-proliferation regime,' Sergei Lavrov told a news conference in Moscow." The Chosun Ilbo reported: "North Korea has apparently restarted a fuel reprocessing facility at Yongbyon. Steam has recently seen coming from the facility. Experts had earlier speculated that it would take two to four months for the North to resume operations at the plant. "Fuel reprocessing extracts plutonium, the raw material for nuclear weapons, from spent fuel rods. North Korea has some 8,000 spent fuel rods at the Yongbyon nuclear facility. If it reprocesses them, it could obtain an additional 6 to 8 kg of plutonium, enough to make one nuclear weapon." This report was later disputed by the Washington-based Institute for Science and International Security. Writing in the Bulletin of the Atomic Scientists, Jeffrey Goldstein said: "perhaps having learned from the long delay that ensued when the new George W Bush administration announced a Korean policy review that produced interminable wrangling within the US government, Pyongyang quickly has ratcheted up the pressure on the Obama administration by threatening to restart its nuclear programme, launching a long-range missile, and now exploding a nuclear device. "Clearly, Pyongyang is trying to force Obama to engage on North Korea's timetable and to focus on the issues that are most important to Pyongyang (namely, ensuring regime survival) rather than those that are most important to Washington (namely, denuclearisation). "By conducting a second nuclear test, North Korea is making the point that, because it's acting as an established nuclear power, the United States needs to give up its focus on putting the North Korean nuclear genie back in its bottle and instead must learn to live with a nuclear North Korea. Possibly spurred by the uncertainty following Kim Jung Il's reported stroke last year, Pyongyang's decision makers appear to have agreed that drastic action designed to bring the United States to the negotiating table on North Korea's terms is worth an adverse reaction from China and the toughening of the Obama administration's initial negotiating position." In Foreign Policy, Donald G Gross wrote: "the United States does not have any good military options for eliminating North Korea's nuclear programme. Quite the contrary: US military action could trigger war on the Korean peninsula, putting at serious risk the lives of hundreds of thousands of South Koreans, not to mention American troops. "What to do? "Energising the Six Party nuclear talks and pursuing vigorous bilateral diplomacy to advance a creative negotiated settlement with North Korea is not just the best option, it is also the only real way to preserve stability in Northeast Asia - the shared goal of the United States and its closest allies in the region, Japan and South Korea, as well as China and Russia. "Rallying the UN Security Council to condemn Pyongyang is a necessary step, but going down the road of simply isolating and imposing further sanctions on North Korea will not achieve the results the US seeks. Pressure on North Korea needs to be coupled with other diplomatic measures that strengthen Pyongyang's sense of security (independent of nuclear weapons) and help reverse its economic decline. "To persuade North Korea to give up its nuclear capability, the United States and the international community must take away that country's best weapon: fear. Through careful calculation and skillful diplomacy, the world can overcome the menace by proving that Pyongyang's desire for security, respect and economic growth are best achieved through other, less hostile means." In The Atlantic, Robert Kaplan wrote: "China ... has good reasons for not wanting to see the kind of North-South Korean conglomerate that might ultimately emerge from collapse [of North Korea]. Reunification of the Korean Peninsula would be, to say the least, geopolitically inconvenient to China. Jutting out far from the Asian mainland, the Korean Peninsula commands all maritime traffic in northeastern China and, most importantly, traps in its armpit the Bohai Sea, home to China's largest offshore oil reserve. Moreover, a unified Korea would likely be nationalistic, with distinctly mixed feelings toward its large neighbours, China and Japan, who have historically sought to control and even occupy it. "And so Kim lives in dread of the Chinese slowly, methodically undermining his regime in a way that will lead to him being replaced - in a palace coup, perhaps - without the implosion of the North Korean state. His only hope is to draw America into direct talks, with Washington implicitly recognizing his regime, so that he can leverage Washington against Beijing. Nuclear tests and missile launches are his own warped way of trying to get the attention of the new Obama administration. He needs to be enough of a problem that Washington will have no choice but to deal with him directly, rather than merely as one party among several in the multilateral talks that have characterised negotiations with North Korea since 2003. "This strategy poses a real problem for President Barack Obama. If he doesn't hit North Korea hard with sanctions, he risks demonstrating to Iran that America is a pushover. Indeed, Obama's Iran policy - which requires the stick of tough action in addition to the carrot of talks and recognition - is on the line in North Korea. On the other hand, vigorous sanctions against North Korea could lead to the collapse of the regime. And anyone who talks breezily about 'helping' North Korea to collapse has simply not learned the lesson of Iraq: The only thing worse than a totalitarian state is no state at all."