Richard Beeston, Diplomatic Editor of The Times, looks at what North Korea is trying to achieve with its latest threat to test a nuclear weapon and how it could affect relations with states across Asia and the rest of the world.

What is North Korea trying to achieve by announcing this now?

The regime in North Korea is very unpredictable and inaccessible, so we have to guess what their motives are. It seems that Pyongyang is suffering from the growing isolation imposed by US sanctions. It would like to break out from the impositions placed on it and have direct talks with Washington. It probably calculates that the only way to get itself heard is to play the nuclear card, which predictably provoked alarm from around the world. America, Britain, France, Japan and South Korea have all condemned the statement by the regime.

How is this announcement likely to affect relations with Western nations?

Western nations are at a loss to know how to respond to Kim Jong-il. His regime is isolated, paranoid and his behaviour is highly eccentric. There is an acceptance that force is not an option in dealing with this problem and that whatever relations with Pyongyang some consideration has to be made to help the destitute North Korean population. The next key step in this process is likely to be the regional summit at the weekend between the leaders of South Korea, Japan and China who will have to find a way of dealing with this problem before North Korea carries out its threat.

What will be the effect on North Korea's relations with its neighbours - South Korea, Japan, China?

China has now responded and taken the unusual step of urging North Korea to "keep clam and restrained on the nuclear test issue". All the regional players are concerned that a nuclear-armed North Korea could change the balance of power in the region and trigger an arms race.

As for Japan, its Prime Minister Shinzo Abe, who has only been in office for a few days, the North Korean threat has presented him with the first crisis of his administration. Japan is already building up a missile defence system and will soon received US Patriot missiles designed to intercept incoming ballistic warheads.

South Korea is likely to try and push the issue higher up the list of global priorities. It will be well placed to do this when Ban Ki-Moon, the South Korean Foreign Minister and a veteran of North Korean talks, is expected to be confirmed as the next United Nations Secretary General. Yu Myung-Hwan, the South Korean deputy foreign minister, even raised concerns that a North Korean nuclear test could prompt Japan to build a nuclear weapon of its own.

What is the next likely/possible course of action?

It is possible that an envoy will be sent to Pyongyang to persuade the regime to change its mind. If the North Korea goes ahead with a nuclear test the consequences could be very serious for the region. It would likely accelerate a defence build up in Japan and South Korea and possibly force China to take a more proactive role in regional security.

What will happen to the agreement made in September last year at six-party talks?

North Korea walked out of the six-party talks nearly a year ago and has refused to return to the negotiating table until America lifts its financial sanctions. In July the North Koreans test fired their new Taepodong-2 surface to surface missile and fired other ballistic missiles. It is widely assumed that the six-party talks remain the only forum which can resolve this stand-off.

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