It had long been taboo for any Japanese politician to discuss the possibility of Japan going nuclear, especially with the country sitting under the protection of the U.S. nuclear umbrella.

As recently as 1999, Defense Agency vice minister, Shingo Nishimura was fired for suggesting there might be nuclear weapons in Japan's future.

In recent years such comments have not been career-ending utterances. And among those making the once taboo statements are not just hawkish members of the conservative governing coalition, but some leading lawmakers in the main opposition party, as well.

The change has come in wake of what are regarded here as hostile intentions by North Korea, its nuclear weapons development program, the test firing of missiles over Japan and clashes between the Japanese Coast Guard and North Korean spy ships.

There is also a rising mood that Japan eventually might not be able to or should not rely on the American nuclear umbrella.

The director of policy studies at Japan's National Institute for Research Advancement, Akiko Fukushima, is an advocate of discussing the nuclear option.

"We shouldn't negate our option to go nuclear," said Akiko Fukushima. "But I do not see any reasonable reasons for Japan to go nuclear at this point of time. If U.S. decides not to provide nuclear deterrence to Japan then [at] that time we have to make a very difficult decision."

Some analysts say the contemporary discussion about a nuclear-armed Japan also results from the perception that countries without such weapons are not being taken seriously on the world stage. Professor Matake Kamiya teaches at Japan's National Defense Academy.

"That kind of attitude taken by major powers in the world could drastically alter the calculation in the minds of the Japanese people," he said.

Public opinion surveys have consistently indicated that around 80 percent of Japanese oppose their country going nuclear, even if the security alliance between Tokyo and Washington were to end.

When he was chief cabinet secretary, Yasuo Fukuda - a longtime confidant of Prime Minister Junichiro Koizumi - once commented that "depending upon the world situation, circumstances and public opinion could require Japan to possess nuclear weapons."

Experts have little doubt Japan could quickly produce its own nuclear arsenal, perhaps within a year. Japan's domestic atomic power program is based on reprocessed plutonium. Technology and capital would also not be a problem for the world's second largest economy.

Lawmaker Ichiro Ozawa, now a leading figure in the opposition Democratic Party, has previously warned if China were to be perceived as a nuclear threat to Japan then Tokyo could respond by making "several thousand" nuclear weapons, making the country an unbeatable military power.

But professor Kamiya says despite the potential nuclear threats in the region, there would be little for Japan to gain by having its own such weapons.

"For this country, even militarily, nuclear weapons actually don't bring much benefit," he said. "Because of my argument like this I have been strongly criticized by so-called right wing conservative people in this country."

Professor Kamiya and others argue if Japan turned its back on the nuclear proliferation treaty - which it ratified in 1976 - that would totally destroy its diplomatic legacy of advocating the abolition of such weapons. But there is a loophole in the treaty, allowing a signatory state to withdraw if "extraordinary events" jeopardize its "supreme interests."

Yoshihide Soeya, a professor of political science at Keio University who has been consulting on Japan's 21st century defense goals, agrees there is little point for Japan to have nuclear weapons.

"I can't think of any possibility of Japan actually going nuclear, even though I understand the topic will remain, perhaps, real in the minds of many people," he said.

Japan's government, at least behind the scenes, seems to have less of an aversion to nuclear weapons than stated in its non-nuclear principles. In recent years, secret agreements have been uncovered by researchers showing Tokyo has permitted U.S. nuclear warheads to be kept on Japanese territory and unloaded at American naval bases in the country.

This seeming contradiction can be best explained if one understands the Japanese concepts of "honne" and "tatemae", which are integral parts of social behavior here. Honne is the actual truth of a matter, which is not expressed openly to maintain tranquility. Tatemae is a kind of polite or tactical facade but without the negative ramifications in this society of what non-Japanese might consider deception.

Proponents of the nuclear option seem to be quietly biding their time awaiting changes in the geopolitical situation.