North Korea is raising the stakes in its nuclear standoff with the United States by vowing to build a light water reactor using indigenous fuel, analysts said Tuesday.

Even though it lacks the technology to build such a plant, they said, the communist state is indicating it will speed up uranium enrichment for nuclear weapons unless Washington softens its attitude.

The North "will witness the appearance of a light water reactor power plant relying on its own nuclear fuel in the near future in the 2010s", the official Korean Central News Agency (KCNA) said in a commentary late Monday.

Light water reactors are more resistant to proliferation than gas-graphite types such as the North's Yongbyon, but use low-enriched uranium as fuel.

The commentary "strongly suggests Pyongyang will speed up a nuclear weapons programme based on highly enriched uranium as it said last year," said Kim Tae-Woo of the Korea Institute for Defence Analyses (KIDA).

The announcement bolsters Pyongyang's assertion last September that it was in the final stages of experimental uranium enrichment, he said.

"Light-water reactors use (low) enriched uranium but it's quite easy for North Korea to turn it any time into a nuclear weapons programme based on highly enriched uranium," Kim told AFP.

US envoy Stephen Bosworth said in December after visiting Pyongyang that the North had agreed to discuss its enriched uranium programme whenever the stalled six-party nuclear disarmament talks restart.

"The North is airing its technology related to uranium enrichment for nuclear weapons before going back to the six-party forum," said Baek Seung-Joo, another KIDA analyst.

"Light water reactors and uranium enrichment may become a hot topic if North Korea return to the dialogue table."

The North quit the talks last April and vowed to restart its longstanding programme to produce weapons-grade plutonium at Yongbyon.

In September it acknowledged for the first time that it also has an enriched uranium programme -- a second way to make atomic weapons.

A full-scale enriched uranium programme is seen as a long-term prospect, but potentially troubling because it could easily be hidden from spy satellites.

The communist state has two preconditions for returning to the forum grouping the two Koreas, Japan, China, Russia and the United States.

It wants a US commitment to discuss a permanent peace pact, and the lifting of United Nations sanctions. Washington says it must first return to nuclear dialogue and show seriousness about honouring past disarmament pledges.

The KCNA commentary described the Obama administration as reluctant to take the initiative in negotiations for fear of being seen as weak before the mid-term elections.

It said the United States justified its doctrine of "strategic patience" towards the North by suggesting that the Pyongyang government may not last.

But the North "has a firm foundation of the independent national economy, which remains solid despite any storm from outside", KCNA said.

Several analysts said the impoverished North does not have the technology to build a light water reactor power plant.

"The commentary is rather seen as a warning that Pyongyang is ready to take further steps unless Washington changes its policy," Dongguk University professor Kim Yong-Hyun told AFP.

Pyongyang is increasingly impatient with Washington's lukewarm response to its demands, he said. "It is telling the outside world that fuel for light water reactors can be enriched to make nuclear weapons."