American Secretary of State Colin Powell wrapped up a four-day Asian trip this week with scant sign of having enlisted South Korea, Japan or China in the United States' approach to resolving North Korea's nuclear brinkmanship. Worse, for a Bush administration poised for war against Iraq, the North Korean government raised the ante again in a showdown that could spark an arms race in East Asia and beyond. US satellites detected a steam plume showing North Korea had activated a five-megawatt reactor mothballed under a 1994 non-proliferation pact with the United States. Only hours earlier, over the Pacific Ocean on his way home, Mr Powell said North Korea had made a 'wise choice, if it's a conscious choice', not to restart the reactor. Still, the US played down the event, just as it had belittled North Korea's launch of a short-range missile that fell into the Sea of Japan on Monday, hours before the inauguration of Roh Moo-hyun as South Korea's president. US President George W. Bush remained focused on a new UN Security Council resolution to pave the way for war on Iraq. 'With each step it takes to advance its nuclear capability, North Korea further isolates itself from the international community,' said Sean McCormack, a White House National Security Council spokesman. Of the cruise missile launching, Mr Powell - in Seoul for Mr Roh's inauguration - said it was not 'particularly surprising or shocking or disturbing'. The latest tensions erupted in October after the US confronted North Korea with evidence of a secret uranium enrichment programme and cut heavy-fuel oil supplies. Since then, the North Korean government has removed international safeguard seals at its Yongbyon nuclear research centre, ordered out UN inspectors and quit the nuclear Non-Proliferation Treaty - the only country ever to do so. Despite its unruffled exterior, the US was expected to move as many as 24 long-range B-52 and B-1 bombers to Guam to deter any North Korean military adventurism if US-led forces invaded Iraq - another issue on which Mr Powell picked up little visible support during his East Asian tour. The bombers were put on alert last month by Defence Secretary Donald Rumsfeld. In its next major step to force the issue, North Korea could begin separating plutonium from stored spent-fuel rods, giving it the makings of as many as six to eight nuclear weapons in as little as six months. In the March-April issue of the Bulletin of the Atomic Scientists, atomic historian Robert Norris, of the Natural Resources Defence Council, and co-authors wrote: 'It is highly unlikely that North Korea will agree to abandon the very thing that gives it leverage with its neighbours and the US.' North Korea's actions could prompt Japan to undertake a nuclear weapons programme, spur China, India and Pakistan, and cause repercussions in Taiwan and South Korea, both of which had nuclear weapons programmes before US pressure forced their termination. But perhaps the larger danger is that North Korea, tagged by the CIA as the world's biggest missile technology peddler, could sell plutonium, highly enriched uranium or finished weapons to other countries or terrorists - a new challenge to the US-declared war on terror.