CHOLSAN, North Korea/SEOUL (Reuters) - North Korea has readied a rocket for a launch from a forested valley in its remote northwest this week that will showcase the reclusive state’s ability to fire a missile with the capacity to hit the continental United States.

Pyongyang says the rocket, to be launched this week, will only carry a weather satellite, but South Korea and the United States say it is a test of a ballistic missile. And although the risk of it veering off course is low, guidance remains its weakest point.

In a rare move, reporters were taken to the new Sohae launch station, close to the border with China, where work was in progress to ready the 30-metre high Unha-3 rocket and its satellite.

The three-stage rocket was on the launch platform, indicating the launch will go ahead on plan between April 12-16.

“Supreme Commander Kim Jong-un made a very bold decision, that is why you are allowed to be this close to the launch site,” site director Jang Myong Jin told visiting foreign journalists on Sunday.

North Korea announced plans to launch the satellite-bearing rocket to coincide with the 100th birthday celebrations of its founder, Kim Il-sung, a move that will help cement the prestige of his grandson Kim Jong-un, who took power in December.

The second stage booster is planned to separate in the seas to the west of the Philippines, about 3,000 km (1,860 miles) from the launch site, and experts say that represents the first possible landfall for the rocket if things go wrong.

If North Korea does achieve a successful separation of the third stage - something it says it achieved in 2009, but most experts say failed to put a previous satellite into orbit - that would show it had improved its technology and the capacity to produce a missile that could carry an intercontinental nuclear warhead.

Pyongyang has also shifted its launch site, and the new, more sophisticated site on the west of the Korean peninsula reduces the risk of debris falling on Japan, which was overflown in a previous test-launch of a missile.

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Graphics on North Korea's rocket and missiles: link.reuters.com/fyg57s

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This launch will take the rocket down the west coast of the Korean peninsula. Japan, which fears a repeat of a 2009 firing over its territory, has put its missile batteries on alert to shoot the rocket down.

“They have come pretty far on the question of range, but they still need a lot to resolve in the precision technology needed for (warhead) re-entry and guidance,” a South Korean military official who spoke on condition of anonymity said.

The Unha-3 is likely the same three-stage liquid-fueled ballistic missile the North fired in 2009 over Japan which eventually splashed down after a 3,800 km flight, military experts in South Korea said.

The new rocket is believed to have a design range of more than 6,700 km (4,160 miles), and can carry a payload of up to 1,000 kg.

At its closest point, Alaska in the United States is about 5,000 km from North Korea.

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The launch will be the first at the Sohae rocket station, construction of which began in 2007. It is a large, sophisticated facility with specialized assembly and transport, according to analysis from military specialist consultancy IHS Jane’s Defense Weekly.

LITTLE RISK

While most international observers doubt that the Unha-2 rocket launched in 2009 managed to put a satellite into orbit, few experts believe there is a high risk the Unha-3 will land on a densely populated urban area.

The biggest risks are a massive failure of the guidance system that could send the rocket north over China, the North’s main political and economic backer, or the destruct mechanism not functioning if it does veer off course, said Markus Schiller from Schmucker Technologie in Munich, an expert on North Korean missile systems.

“There always is a residual risk, of course, that several things might go wrong and lead to unforeseen disaster ... but this risk is very low, actually approaching zero,” Schiller said in an emailed response to questions.

“It is far more likely that the rocket itself fails and blows apart.”

The launch site is located 50 km (30 miles) from North Korea’s border with China.

“The worst case scenario is it strays into China or South Korea if the rocket goes out of control,” said an expert on rocket technology at a South Korean state-run research institute, who spoke on condition of anonymity due to the sensitivity of the issue.

While North Korea’s 23 million people live in poverty and many are at risk of malnutrition, the prestige of developing rocket technology and nuclear weapons capacity is the most important issue for Pyongyang, which sees it as a deterrent against invasion.

The North is believed to have stockpiled enough fissile material to manufacture up to 10 nuclear bombs and South Korea’s Yonhap news agency said on Sunday it was preparing for a third nuclear test.

Government officials in South Korea have calculated the North is spending $19 million on this launch.

“I believe North Korea is developing many technologies simultaneously - technologies on rocket that can deliver nuclear warheads, materials that can cope with high temperature when reentering the atmosphere and on the miniaturization of nuclear bombs,” said the South Korean rocket expert.