WASHINGTON - VICE-PRESIDENT Joe Biden on Sunday committed the US to enforcing new UN penalties against North Korea while acknowledging that 'God only knows' what ruler Kim Jong Il wants from the latest showdown.

The sanctions are aimed at depriving the reclusive communist country of the financing used to build its nuclear programme. A new UN resolution also authorises searches of North Korean ships suspected of transporting illicit ballistic missile and nuclear materials.

'It is important that we make sure those sanctions stick and those sanctions prohibit them from exporting or importing weapons,' Mr Biden said. 'This is a matter of us now keeping the pressure on.'

Ahead of President Barack Obama's meeting on Tuesday in Washington with South Korean leader Lee Myung Bak, the North warned of a nuclear war on the Korean peninsula and pledged to step up its atomic bomb-making programme in defiance of the fresh penalties.

'They say a lot of things,' Mr Biden said in an interview with NBC television's 'Meet the Press.' He called the North 'a destabilising force in the region.'

'There is a coalescing of that conclusion on the part of the Chinese, the Russians, Japanese, South Koreans, Americans like never before,' Mr Biden said. These countries have been involved in negotiations with North Korea to curb its nuclear weapons programme.

On Saturday, North Korea said it has been enriching uranium to provide fuel for its light-water reactor. It was the first public acknowledgment that the North is running a uranium enrichment programme in addition to its known plutonium-based programme. The two radioactive materials are key ingredients in making atomic bombs.

'God only knows what he wants,' Mr Biden said of Mr Kim. 'There's all kinds of discussions. Whether this is about succession, wanting his son to succeed him. Whether or not he's looking for respect. Whether or not he really wants a nuclear capability to threaten the region. ... We can't guess his motives.'

'We just have to deal with the reality that a North Korea that is either proliferating weapons and or missiles, or a North Korea that is using those weapons ... is a serious danger and threat to the world, and particularly East Asia,' the vice-president said.

Further adding to the tensions, North Korea last week handed down 12-year prison terms to two detained American journalists. Asked about potential negotiations for their release, Mr Biden said, 'I don't think it's appropriate, nor in the interests of the journalists, for me to discuss that.' -- AP