If the international community's main goal is to push North Korea towards denuclearisation, does the fact that Pyongyang is racing in precisely the opposite direction suggest a fundamental policy failure?

The question has taken on added urgency following a succession of monthly warnings sounded by satellite imagery analysis that the North's nuclear weapons programme is gathering pace.

In August, images suggested the North had doubled its uranium enrichment capacity at its Yongbyon nuclear complex.

In September, they indicated it had re-started the plutonium reactor that provided the fissile material for at least two of its three nuclear tests, and just last week they pointed to preparatory work for another detonation at its nuclear test site.

"Pyongyang is moving ahead on all nuclear fronts," believes US nuclear scientist Siegfried Hecker, a leading expert on the North's weapons programme.

Since coming to power in late 2011 following the death of his father, North Korea's young leader Kim Jong-Un has overseen a successful long-range rocket launch and the North's third -- and largest -- nuclear test.

"Denuclearisation must remain the goal, but it is a more distant one following these new developments," Hecker wrote in the Bulletin of the Atomic Scientists.

If there is clear agreement on where the North is heading, there is little consensus on how best to stop it getting there.

The key question for the international community is the same as it has always been -- whether to engage with Pyongyang or not.

Both North Korea and its main ally China want a return to six-party talks grouping China, the two Koreas, Japan, Russia and the United States.

Washington and Seoul are adamant that Pyongyang must first demonstrate a commitment to denuclearisation, but the North has repeatedly stated it has no intention of abandoning its weapons programme.

Road to WMD development 'wide open'

The result is almost total impasse at a time when the North is making possibly its greatest strides towards achieving a credible nuclear deterrent.

"There is no diplomatic mechanism in place today that offers any prospect for slowing or stopping the North's WMD programmes," former senior US State Department official Evans Revere said in a paper published this month by the Washington-based think-tank Brookings Institution.

"The road to further development of these programmes by North Korea is now wide open, and Pyongyang is taking it," Revere said.

Supporters of the principle of no substantive dialogue without prior progress on denuclearisation argue that to do otherwise would be tantamount to accepting Pyongyang's recent progress towards nuclear statehood.

"Returning to talks now... would allow North Korea to have reset the table for negotiations in a way that undercuts the goals of North Korean nuclear disarmament," said Paul Haenle, a former US representative at the six-party dialogue.

At the same time, Haenle, now the director of the Carnegie-Tsinghua Center for Global Policy in Beijing, noted that dialogue with Pyongyang in the past at least had the merit of slowing the North's weaponisation programme down.

Since the last six-party talks in December 2008 the brakes have clearly been taken off, with the North conducting two nuclear tests, revealing a uranium enrichment facility and putting a satellite in orbit with a launch widely seen as a ballistic missile test.

International sanctions have been expanded but, despite increased cooperation from China, they still lack the intensity to present Pyongyang with a choice between nuclear weapons and economic survival.

Barring a sudden implosion of the regime, Revere believes talks are the only real option -- and at the very highest level.

"If the goal is to convince North Korea to implement its denuclearisation commitments, nothing short of a dialogue with the North's leader or his inner circle is likely to achieve this," he said.

Kim Jong-Un: a risk taker?

Nearly two years after taking over, Kim Jong-Un remains something of a mystery, although most experts agree he has successfully negotiated the tricky power transition.

Initial hopes that he had a reformist bent have since withered, but long-time North Korea watcher Andrei Lankov believes the young leader will have to take risks spurned by his father, Kim Jong-Il, if he wants to stay in power.

Kim Jong-Il was nearly 60 by the time he had consolidated his leadership after the death of his father Kim Il-Sung.

The North's economy was already in dire straits, but reform carried risks for stability and Lankov argues that Kim gambled on the system outlasting him even if he did nothing.

"Dying a natural death was Kim Jong-Il's major strategic goal, and he achieved it," said Lankov, a professor at Kookmin University in Seoul.

By contrast, the 30-year-old Kim Jong-Un -- his exact age is disputed -- will have to gamble on some economic reforms if he wants to remain where he is into old age.

But reforming such a tightly-controlled economy risks destabilising the Kim dynasty's hold on power and could usher in a period of national vulnerability that the regime believes is best negotiated with a nuclear deterrent.

"The bad news is that a reforming North Korea will remain nuclear," Lankov told a recent conference on North Korea held in Seoul.

"The North Korean regime believes nukes are important precisely because reforms make them less stable," he added.