Foreign Minister Taro Aso, who has called for discussion of Japan's non-nuclear policy, also asserted that the pacifist constitution does not forbid possession of the bomb.

"Japan is capable of producing nuclear weapons," Mr. Aso told a parliamentary committee on security issues. "But we are not saying we have plans to possess nuclear weapons."

Of course, Aso was only stating the obvious. Japan has long had the technical ability to build a bomb. It also has an extensive nuclear energy program, which supplies about 20 percent of the country's energy needs. In addition, the country has spent years studying the use of fast breeder reactors for the production and reprocessing of plutonium.

In practice, Japan relies on the U.S. nuclear umbrella to deter foreign attacks. And Article 9 of Japan's Constitution states in part that "the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes." On the other hand, Article 9 also says that "land, sea, and air forces, as well as other war potential, will never be maintained," but that hasn't stopped the Japanese from building up it's land, sea and air forces.

Strictly speaking, these forces are viewed as extensions of the national police force, to be used solely for maintaining law and order. However, many Japanese politicians have advocated amending Article 9 by adding a clause that would authorize the use of military force for the purpose of "self-defense." The problem, of course, is that actions taken in self-defense can be viewed differently by other countries. For example, if North Korea was preparing to launch a missile in Japan's direction, would Japan be acting in self-defense if it attacked first?

So far the consensus in Japan has been to leave Article 9 alone. But Aso's comments are a clear warning to North Korea and its patron, China: provoke us at your peril.