Movement around an atomic test site in North Korea indicates the reclusive state may stage another nuclear test, a South Korean minister said today, as one of its military leaders postponed a trip to Washington DC because of the escalating security situation in the region

The warning from South Korea's Unification Minister, Ryoo Kihi-jae, came after Pyongyang moved a missile battery to the east coast last week after repeatedly threatening a strike on US targets in Guam, Hawaii and even the west coast of America. The relocated missile is thought to be a Musudan, which has a range of more than 3,000km, putting Guam within reach.

General Jung Seung-jo, chairman of South Korea’s joint chiefs of staff, said he had delayed a meeting with his opposite number in America, General Martin Dempsey, as he wished to remain in South Korea while tensions were high. The news came as the US postponed a test of its own long-range ballistic missile, due to be launched from California, for fear of inflaming the crisis still further. US reports said the Defence Secretary, Chuck Hagel, had delayed the Minuteman 3 test until “some time next month”, but joint war drills with the South Korean military near the border with the North would continue.

Download the new Independent Premium app Sharing the full story, not just the headlines

With the West continuing to press Beijing to use its political leverage against Pyongyang, the Chinese President Xi Jinping appeared to take a swipe at both sides. Speaking in front of world leaders at a forum in southern China, Mr Xi said “no one should be allowed to throw the region, or the whole world, into chaos for selfish gains”.

Most observers believe Pyongyang’s fierce rhetorical barrage since last week is a political power-play by the government of Kim Jong-un, mainly for domestic consumption, but few are ruling out the possibility of events spinning out of control. British Foreign Secretary, William Hague, became the latest politician to call for calm, pleading with Mr Kim’s regime to pull in its horns. “We have to be concerned about the danger of miscalculation by the North Korean regime,” he said. The Cuban leader Fidel Castro, a friend of the Pyongyang regime, recently described the face-off as one of the “gravest risks” for nuclear war since the 1962 Cuban missile crisis.

Seoul has continued to play down the threat of war, but in a sign that it is taking nothing for granted, the Defence Minister, Kim Kwan-jin, has recommended withdrawing South Korean workers from the Kaesong industrial complex across the border.

The jointly run complex is the last remaining lifeline between the two sides and an important source of income for Pyongyang. “If any North Korean provocation were followed by retaliation, the workers could be held hostage,” Mr Kim said. About 120 South Korean firms operate in the complex and 500 nationals are reportedly inside. Last week North Korea closed the border to Kaesong.

Yesterday, the South’s government predicted the North could test a missile this week, ahead of a visit by US Secretary of State, John Kerry, on Friday. A spokeswoman for the government, Kim Haeng, said the South’s military was in “readiness” mode. The North is likely to use America’s cancellation of its Minuteman 3 test for propaganda purposes, arguing Washington blinked first. But the crisis is unlikely to end there. “The show of strength and ambitions will continue until someone pushes a wrong button,” said Leonid Petrov, a Korea expert at the Australian National University.