The North Korean nuclear crisis has alarmed countries throughout the Asia-Pacific region, including Japan. Some Japanese politicians are suggesting Japan develop its own nuclear arsenal in response, an idea which most Japanese citizens reject.

Concerns about North Korea's nuclear weapons program have been rising since October, when Washington says Pyongyang admitted to running a program to enrich uranium, which can be used for nuclear weapons. Since then, the North has engaged in a series of acts which have rattled Japan, including withdrawing from the nuclear Non-Proliferation Treaty and testing short-range missiles in nearby waters.

The two countries do not have diplomatic relations, but, at a summit last year, they signed an agreement to work towards normalizing ties and pledged not to threaten each other's security. Japanese government spokesman Yasuo Fukuda warned Wednesday that Tokyo could withdraw from the pact, if the North attacks Japan.

"If we abandon it, it is unclear what will happen to Japan's relationship with North Korea. We will have to proceed carefully," he said.

Concerns are rising in Japan that North Korea will test a long-range missile, taking advantage of Washington's distraction with the Iraq crisis. Most Japanese know that many of their large cities lie within range of North Korea's missiles and that a rocket fired from Pyongyang would take less than ten minutes to reach downtown Tokyo.

Although there are doubts about the accuracy and effectiveness of the North's weapons, military experts warn that parts of Japan could be devastated if its missiles were armed with chemical, biological or nuclear warheads.

Derek Mitchell is a senior fellow at the Center for Strategic and International Studies in Washington. He says worries over North Korea could soon prod Japan into its own military build-up.

"I think the initial reaction towards this missile threat from North Korea has been and will be acceleration of research and development with the United States of missile defense," Mr. Mitchell said. " That might not be enough, though, and I'm not sure they will feel comfortable entirely with remaining simply under the umbrella of the United States. They may seek to have their own capabilities, so they can take care of their own defense."

Some right-wing politicians in Japan want the government to build nuclear weapons to counter any aggressive action from the North. The country certainly has the financial means to do so, with a defense budget of $40 billion a year - the world's second-largest after the United States. Japan also has vast stocks of reactor-grade plutonium, generated by its nuclear-energy program. That is enough for hundreds, if not thousands of weapons.

But even in the face of what Japan sees as a growing nuclear threat from North Korea, such a move is considered highly unlikely. As the only nation ever to be attacked with nuclear weapons, the concept has very little public support. Memories of the U.S. atomic bombs that fell on the cities of Hiroshima and Nagasaki remain vividly painful and the country still suffers from what is commonly known as kaku alleroogee or a "nuclear allergy."

"Japan's people do not have any kind of will to have nuclear weapons by ourselves. We depend for deterrence on the U.S. nuclear umbrella," said Toshiyuki Shikata, a retired Japanese general.

But Professor Shunji Yanai, of Tokyo's Chuo University, warns sentiment could shift, if the nuclear situation on the Korean Peninsula continues to escalate.

"We are strongly committed to non-nuclear policy in this country for historical and also strategic reasons too. But if North Korea has gained nuclear weapons and improved its means of delivery, it might have a very strong impact on Japanese public opinion," he said.

Public sentiment is not the only hurdle in Japan. The country has a pacifist constitution, which was designed by the United States, following the World War II, to stop Japan from re-emerging as a military power. Although the nation has a 160,000 troop self-defense force, laws restrict its ability to act, except to protect sovereign Japanese territory. Japan's soldiers have not seen combat since World War II.

Amending the constitution to boost Japan's offensive military capabilities and create a nuclear weapons program would be difficult. Two-thirds of parliament would have to back such a move, as would a majority of people voting in a national referendum.

So, although a shift to a nuclear Japan appears distant and unlikely, the tensions over North Korea's nuclear, biological and chemical weapons could trigger some sort of regional arms race and has Japanese leaders thinking seriously about how best to protect the nation.

Tokyo is preparing to launch its first two "spy" satellites, later this month, and, in a joint project with Washington, is also speeding up the development of a missile-defense system. This year, Japan will also establish a special military unit to defend cities against guerrilla attacks - partly because of the North's vast special forces, which could potentially threaten these key areas.