North Korea dramatically escalated its warlike rhetoric on Thursday, warning that it had authorised plans for nuclear strikes on targets in the United States.<\/span><\/p>\n <\/span><\/p>\n “The moment of explosion is approaching fast,” the North Korean military said, warning that war could break out “today or tomorrow”.<\/span><\/p>\n <\/span><\/p>\n Pyongyang’s latest pronouncement came as Washington scrambled to reinforce its Pacific missile defences, preparing to send ground-based interceptors to Guam and dispatching two Aegis class destroyers to the region.<\/span><\/p>\n <\/span><\/p>\n Tension was also high on the North’s heavily-fortified border with South Korea, after Kim Jong-Un’s isolated regime barred South Koreans from entering a Seoul-funded joint industrial park on its side of the frontier.<\/span><\/p>\n <\/span><\/p>\n In a statement published by the state KCNA news agency, the Korean People’s Army general staff warned Washington that US threats would be “smashed by… cutting-edge smaller, lighter and diversified nuclear strike<\/a> means”.<\/span><\/p>\n <\/span><\/p>\n “The merciless operation of our revolutionary armed forces in this regard has been finally examined and ratified,” the statement said.<\/span><\/p>\n <\/span><\/p>\n Last month, North Korea threatened a “pre-emptive” nuclear strike against the United States, and last week its supreme army command ordered strategic rocket units to combat status.<\/span><\/p>\n <\/span><\/p>\n But, while Pyongyang<\/a> has successfully carried out test nuclear detonations, most experts think it is not yet capable of mounting a device on a ballistic missile capable of striking US bases or territory.<\/span><\/p>\n <\/span><\/p>\n Mounting tension in the region could however trigger incidents on the tense and heavily-militarised border between North and South Korea.<\/span><\/p>\n <\/span><\/p>\n There was no immediate American reaction to the North’s latest statement, but US Defense Secretary Chuck Hagel<\/a> said Pyongyang represented a “real and clear danger” to the United States<\/a> and to its allies South Korea and Japan.<\/span><\/p>\n <\/span><\/p>\n “They have nuclear capacity now, they have missile delivery capacity now,” Hagel said after a strategy speech at the National Defense University. “We take those threats seriously, we have to take those threats seriously.”<\/span><\/p>\n <\/span><\/p>\n “We are doing everything we can, working with the Chinese and others, to defuse that situation on the peninsula. I hope the North will ratchet its very dangerous rhetoric down,” he said.<\/span><\/p>\n <\/span><\/p>\n The Pentagon<\/a> said it would send ground-based THAAD interceptor batteries to protect US bases on the island of Guam, complementing two Aegis anti-missile destroyers already dispatched to the region.<\/span><\/p>\n <\/span><\/p>\n The THAAD (Terminal High Altitude Area Defence) is a truck-mounted system that can pinpoint an enemy missile launch, track the projectile and launch an interceptor to bring it down.<\/span><\/p>\n <\/span><\/p>\n Guam is a US island territory 3,380 kilometres (2,100 miles) southeast of North Korea in the Pacific and is home to 6,000 American military personnel, as well as bases for submarines and strategic bombers.<\/span><\/p>\n <\/span><\/p>\n The new defensive measures came as Pyongyang stopped South Korean staff members from entering the Kaesong complex, a shared industrial zone funded by Seoul but 10 kilometres inside the North.<\/span><\/p>\n <\/span><\/p>\n Pyongyang said the 861 South Koreans already in the zone could leave, but the move cut the last practical cooperation between the rival powers and was seen as a dramatic escalation in the crisis.<\/span><\/p>\n <\/span><\/p>\n South Korea’s defence ministry said it had contingency plans that included “military action” if the safety of its citizens in Kaesong was threatened.<\/span><\/p>\n <\/span><\/p>\n China, the North’s sole major ally, appealed for “calm” from all sides and Russia’s Deputy Foreign Minister Igor Morgulov said he was worried that the situation could spiral out of control.<\/span><\/p>\n <\/span><\/p>\n Describing the Kaesong ban as “very regrettable”, South Korea’s Unification Ministry urged the North to normalise access immediately.<\/span><\/p>\n <\/span><\/p>\n “Otherwise,” the ministry warned, “not only will inter-Korean relations be negatively affected but North Korea will invoke greater criticism and isolation from the international community.”<\/span><\/p>\n <\/span><\/p>\n It said 33 South Koreans had returned from Kaesong, with hundreds staying on to keep their companies running smoothly.<\/span><\/p>\n <\/span><\/p>\n Around 53,000 North Koreans work at 120 South Korean plants at the complex, which was still operating normally Wednesday.<\/span><\/p>\n <\/span><\/p>\n Tensions have soared on the Korean peninsula since December, when the North test launched a long-range rocket. In February, it upped the ante once again by conducting its third nuclear test.<\/span><\/p>\n <\/span><\/p>\n Washington has deployed nuclear-capable US B-52s, B-2 stealth bombers and two US destroyers to South Korean air<\/a> and sea space.<\/span><\/p>\n <\/span><\/p>\n This week, the North warned it would reopen its mothballed Yongbyon reactor — its source of weapons-grade plutonium. The North shut down Yongbyon in July 2007 under a six-nation aid-for-disarmament accord.<\/span><\/p>\n