North Korea has taken the rare step of showing off a rocket-launching site to foreign journalists.
Pyongyang says the rocket, to be launched this week, will only carry a weather satellite.
South Korea and the United States say the real aim is to test a ballistic missile.
According to the North Koreans, the satellite will provide images and other information useful for weather forecasts. The official reason for the launch is to celebrate the 100th birthday of the country’s founder Kim Il-sung – a move that could help boost the prestige of his grandson who took power in December.
The South Koreans say new satellite images show the North is planning a third nuclear test.
“We want to clarify that it (the launch) is a provocation that threatens the peace and stability of the Korean peninsula and northeast Asia. We (the South Korean military), are fully prepared to protect the South Korean people,” said South Korean Defence Ministry spokesmanKim Min-seok.
Japan, fearing a repeat of a launch in 2009 over its territory, has put its missile batteries on alert. Tokyo, like Seoul, has threatened to shoot the rocket down if it strays into its territory.
But it is thought the location of the launch site near the border with China reduces the risk of debris falling on Japan.
Several western countries have warned North Korea against the launch, warning that it would violate UN resolutions.