Is North Korea close to weaponising a long-range rocket?

Washington: While a defiant North Korea on Sunday claimed that its space programme is for peaceful purposes, many analysts worry that it is designed to mask testing of inter-continental ballistic missiles (ICBM) that could threaten the US mainland.

Developing successful ICBM technology capable of transporting a nuclear payload accurately over vast distances is no easy feat. It demands sophisticated technology only achieved through intensive testing, experts say.

Testing rockets through satellite launches would provide invaluable data for potential future ICBMs, according to a 2015 report on Pyongyang's space programme by 38 North, an analysis website run by the US-Korea Institute at Johns Hopkins University.

"Even failed satellite launches would be a learning experience," CNN quoted aerospace engineer John Schilling as saying.

Schilling said that a key sign to look out for in future North Korean satellite launches would be attempts to test an advanced re-entry vehicle, vital for an effective ICBM.

North Korea's state TV today announced the nation has successfully put a satellite into orbit, "legitimately exercising the right to use space for independent and peaceful purposes".

Experts say a key step towards a successful ICBM programme would be miniaturising nuclear weapons, making them light enough to fit on top of a rocket.

Pyongyang claimed in May last year that it had successfully miniaturised a nuclear weapon, in an announcement that was met with skepticism from US officials.

While the White House was adamant that North Korea did not yet have the capability, other experts were not so sure.

US Army General Curtis Scaparrotti, the commander of US forces in Korea, had said in October 2014 that he thought Pyongyang was capable of miniaturising a nuclear device.

Miniaturising a nuclear weapon is one key part of building a nuclear-armed ICBM. The nuclear device also needs to be tough enough to be able to withstand the flight on a ballistic missile, experts say.

The Taepodong rocket, currently under development in North Korea and closely related to the Unha device used to launch Pyongyang's satellites, is believed to have a range of up to 9,000 kilometers, putting most of Western Europe, Asia and the western US under threat.

While an ICBM is vital if North Korea wants to threaten the US mainland, American military bases in Asia are likely well within range of existing technology, to say nothing of Tokyo or Seoul, the capital cities of two key US allies.

Analysts agree that Pyongyang already possesses a nuclear arsenal of around a dozen nuclear weapons.

North Korea has also carried out submarine-launched ballistic missile (SLBM) testing, which would make it far more difficult to detect launch the vehicle. And it would also reduce the range its missiles would need to travel.

If confirmed, such a capability would threaten Hawaii and other US Pacific territories, the report said.