Just a few months ago, it may have been hard to conceive a Japanese headline like 'A Nuclear Japan? No Way, says Abe' - a reflection of both the hawkish demeanour of new Prime Minister Shinzo Abe and the taboo nature of the issue within Japan. But Monday's apparent nuclear test by North Korea has challenged regional security assumptions in all kinds of ways. It has intensified fears of a regional arms race, and pushed Japan's ambitions and interests onto the front burner. Last week this column looked at some of the issues driving a quiet nuclear debate inside and outside Japan as Mr Abe seeks to overturn the nation's pacifist constitution to create a more militarily assertive nation. But the past few days have brought the simmering issue to the boil. Within two days of the test, Mr Abe was forced to move swiftly to ease regional fears. While insisting Japan was prepared to take its own 'tough measures' against Pyongyang, he insisted that going nuclear was not up for discussion. 'We have no intention of changing our policy that possessing nuclear weapons is not our option,' Mr Abe told a parliamentary committee. 'There will be no change in our non-nuclear-arms principles. We want to seek a solution through peaceful and diplomatic means.' In Australia, former prime minister Paul Keating was among the most explicit to voice alarm. 'My great concern is that Japan may use the test to move into nuclear weapons itself, eschewing the nuclear protection provided to it by the United States under its umbrella,' he said. Shortly before the test, former Japanese prime minister Yasuhiro Nakasone helped kick-start the debate through his Institute of International Policy Studies. The think-tank proposed Japan should study nuclearisation 'in preparation for a major change in the international community in future'. The view was picked up by the conservative Yomiuri daily, Japan's largest newspaper. Hedging its bets slightly in an editorial on Wednesday, it stated: 'Needless to say, it is hardly conceivable that Japan possessing a nuclear weapon will become a real issue anytime soon. But North Korea becoming a nuclear-armed country certainly constitutes a 'major change in the international community'. 'The government must not let our country have to fear for its existence by failing to take a realistic response to such a major change, due to its emotional 'nuclear allergy'.' Some foreign observers were quick to play down any threat, pointing to the long-held anti-nuclear sentiment inside Japan, the only victim of an atomic attack. They also stressed that as Japan fell under the protection of the US, developing its own weapons could only harm its interests. On A17 (Insight) today, Brad Glosserman, executive director of the Centre of Strategic and International Studies' Pacific Forum, says nuclearisation would damage the country's image, undermine non-proliferation efforts, spark a regional arms race and damage ties with the US. 'That logic hasn't changed,' he writes. 'A nuclear weapon wouldn't add to Japan's defence capability, but would do real damage to its core security interests. To their credit, the Japanese recognise that.' It is certainly a debate worth watching in the weeks and months ahead. It is a reminder of just how unsettling North Korea's brinkmanship could be, driving all manner of wider ramifications. As some analysts have noted, it underlines the need for the US to reach out before talk of a regional arms race, and pull China, Japan and South Korea together for tough debate on the responsibilities ahead.