Rice warns of Asian nuclear arms race

North Korea's nuclear test could set off an atomic arms race in Asia, US secretary of state Condoleezza Rice warned.

Her comments came at Elmendorf US Air Force base in Alaska, as she departed for Japan, her first stop on a tour devoted almost entirely to answering North Korea's nuclear threat.

In addition to settling nerves among allies, Rice's Asia trip is meant to reinforce pressure on South Korea and especially China to enforce sanctions. Those include what the US describes as an aggressive inspection and interdiction programme that stops short of a full blockade of North Korean trade.

The US is concerned that Japan and South Korea may want to develop their own nuclear weapons programmes to counter the threat from North Korea and part of Rice's assignment on this week's hastily arranged trip to Japan, South Korea, China and Russia is to lessen that temptation.

"Obviously an event of this kind does carry with it the potential for instability in the relationships that now exist in the region," Rice said.

"That's why it's extremely important to go out and to affirm, and affirm strongly, US defence commitments to Japan and to South Korea."

Her diplomatic language refers to the calculus of nuclear deterrents and to the long-standing US pledge to use its own nuclear arsenal to defend its friends.

On her trip, Rice planned to ask South Korea to expand its role in a US-led international programme to stop the spread of weapons of mass destruction, Alexander Vershbow, the US ambassador to South Korea, said in Seoul.

Rice would not comment in detail about worries by the US and other governments that the North may be preparing for a second test explosion.

"We're concerned about further action by the North Koreans," Rice said, "but further action by the North Koreans will only deepen its isolation, which is pretty deep right now."

Concern over a second test stems partly from new satellite imagery showing increased activity around at least two other North Korean sites, a senior defence official said.

The activity, started a number of days ago, included ground preparation at one site and construction of some buildings and other structures, said the official. He said that although the purpose of the structures was unclear, officials were concerned because North Korea had left open the possibility of another test.

The White House said yesterday that it would not be surprising if North Korea were to try another nuclear test "to be provocative".

At the Pentagon, US defence secretary Donald Rumsfeld said that while it was unclear what role the US military might take in enforcing new United Nations sanctions, he did not expect the US or any other nation to do so unilaterally.

"It takes co-operation among a great many countries to participate and things move by land, sea and air, and it's complicated, and only time will tell," he told reporters.