North Korea's latest nuclear test poses a stark challenge to the international community which, analysts say, will struggle to come up with a concerted, effective response, despite the chorus of global outrage at Pyongyang's move.

Condemnation of the North's claim on Wednesday to have tested its first hydrogen bomb has been swift and universal, but the real battle will be converting the indignation into concrete action that has the same across-the-board backing.

While the UN Security Council has agreed to draw up "significant" punitive measures, there seems little consensus on what can effectively be added to the rafts of sanctions imposed on North Korea following its three previous tests in 2006, 2009 and 2013.

Wednesday's test amply demonstrated the ineffectiveness of the sanctions regime to date, and the core debate now is whether the way forward lies in harsher sanctions, dialogue -- or a combination of the two.

Current US policy, backed by ally South Korea is one of "no reward for bad behaviour" and requires North Korea to take a tangible step towards denuclearisation before proper talks can begin -- a pre-condition many view as hopelessly unrealistic.

-- Sanctions 'not working' --

"Sanctions alone just aren't working, we've seen that," said Joe Cirincione, president of the Ploughshares Fund, a global security foundation and author of "Nuclear Nightmares: Securing the World Before It Is Too Late".

"There has to be a path opened to discussions, however difficult that may be to swallow," said Cirincione, who added the current US strategy amounted to little more than the hope that ignoring Pyongyang might make it go away.

"But North Korea is like that Glenn Close character from Fatal Attraction. It will not be ignored," he added.

Pyongyang's claim that Wednesday's test was a sophisticated hydrogen bomb has been largely dismissed by experts, who say the apparent yield was far too low for such a powerful device.

For now, the general consensus is that it could have been a boosted-fission bomb, which would be more powerful than the simply fission implosion devices it tested before, but far short of a genuine two-stage H-bomb.

But whatever device it turns out to be, the message from North Korea is the same -- no matter the cost exacted by the international community, it will continue to develop its nuclear weapons capability.

-- The need for engagement --

"Success in developing simple thermonuclear devices is likely a matter of time and a relatively small number of additional tests," said David Albright, president of the Washington-based Institute for Science and International Security.

"A priority must be to find ways to both further pressure North Korea to limit its nuclear weapons capabilities and engage it diplomatically," Albright said.

There is room to increase pressure by imposing the sort of extensive economic sanctions that helped bring Iran to the negotiating table over its nuclear programme.

But to be effective, these would impact Chinese companies and financial institutions that account for the lion's share of North Korea's overseas business.

China is likely to balk at any such move and Washington would be wary of pushing Beijing at an already sensitive time for relations between the two powers.

And the United States will have trouble enough just coming up with a unified strategy of its own, given the toxic nature of the North Korean issue in election season.

US Republicans have gleefully painted the latest test as another foreign policy failure for President Barack Obama's outgoing administration, and it would be a brave presidential candidate who suggested dialogue with Pyongyang as a way forward.

-- China fears --

China, meanwhile, is unlikely to back any moves that could genuinely destabilise the regime of North Korean leader Kim Jong-Un, given its overriding fear of a reunified, US-allied Korea directly on its border.

"China, no matter how strong the language it uses in its criticism on the North, will not join any Security Council punishment that may have a real impact on the North's regime," said South Korea's former national Security Adviser, Chun Young-Woo.

"And North Korea knows that," he added.

So if China won't back genuinely punitive sanctions, and the US sticks to its policy of not engaging North Korea, the prospect of any new response to the North's latest provocation looks quite bleak.

Cirincione, however, hopes that the shock of the H-bomb announcement -- whether a bluff or no -- might have been enough to push Beijing to increase pressure and Washington to risk exploring a dialogue route.

"And it is a risk, because there's no guarantee negotiations will work. But then nothing else has worked.

"So it just seems the risks of inaction must be greater than the risks of action," he said.