North Korea's decision to launch a missile was not entirely unexpected.

In the past few days, the United States has even moved sophisticated ballistic missile tracking equipment into Japan.

The test also comes just a few weeks after Pyongyang said it would continue to develop, test and export ballistic missiles - its first official admission of a hitherto clandestine trade.

But if this really was a maiden test of the Taepo-dong 1 missile, then alarm bells will be ringing around the region.

More advanced technology

The Taepo-dong is a more advanced version of the Rodong 1 missile which was first tested in 1993.

That test caused huge alarm because it demonstrated that not only South Korea, but also parts of Japan, were easily within the missile's range of at least 1,000km.

South Korean officials and independent defence analysts say the range of the Taepo-dong could be up to twice as long, putting the whole of Japan within its range.

Diplomatically, the missile appears to be aimed squarely at the United States, which has imposed a near total economic embargo on North Korea.

Officials from Pyongyang are currently holding talks in New York on the agreement to freeze the North's nuclear programme in exchange for two new reactors to be built and fuelled by the United States, South Korea, Japan and the European Union.

That agreement has run into trouble, partly because of concern about North Korea's missile exports.

Pyongyang has accused Washington of reneging on the deal.

Raising the stakes

So the missile test could be an attempt by the North to raise the diplomatic stakes.

Pyongyang knows full well that advertising its missile programme to the international market in this way will place enormous psychological pressure on Washington, which is agitated about the proliferation of ballistic missile technology to countries such as Pakistan, India, Iran, Iraq and Syria.

There is also a clear internal logic behind the latest test.

The North Korean leader Kim Jong-il probably calculates that a display of military might will boost his prestige as North Korea prepares for the 50th anniversary of its founding.

The North Korean state enters its second half century in a state of isolation and impoverishment, its population suffering from chronic food shortages.