A North Korean missile could reach central Tokyo in approximately 8.5 minutes, a fact that has the Japanese increasingly worried. In response to these concerns, Tokyo is revamping its defense strategy. The centerpiece is a proposal for a U.S.-designed missile defense shield that would cost about $1 billion annually over the next four years.

Tokyo is considering a two-stage anti-missile system. At sea, SM-3 missiles would be launched from Aegis destroyers, to intercept incoming ballistic missiles. As a second line of defense, advanced Patriot missiles would be stationed on land, first around Tokyo and eventually throughout the country.

Lance Gatling is an American aerospace consultant in Tokyo, who calls the plan "Japan's revolution in military affairs." He points out that Japan's basic military strategy previously was based on old Cold War concerns about a possible invasion by the former Soviet Union.

"The basis for their military spending is changing," he said. "So, they will spend less money on conventional defense, which means tanks, fighters that would attack ground targets, enemy ground targets inside Japan. They are starting to spend money on missile defense and on the intelligence that will help them gather information regarding a possible missile attack from outside the country."

There is no question that North Korea's nuclear ambitions are driving the new defense strategy. Nearly a year ago, U.S. officials said Pyongyang admitted to having a secret nuclear weapons program, in violation of several international accords.

Since then, North Korea has withdrawn from the nuclear Non-Proliferation Treaty and expelled U.N. nuclear inspectors. It has said it needs the weapons program to deter an attack from the United States. Washington has repeatedly denied any intention of an attack.

U.S. officials, working with Japan, China, South Korea and Russia, are demanding Pyongyang immediately abandon its nuclear programs and comply with its international commitments.

The latest multilateral talks in August in Beijing ended without movement in the dispute.

Some conservative politicians and analysts in Japan worry that, if a conflict with North Korea erupts, the Stalinist state could strike Japan first. These fears go back nearly a century, as Japan is still widely hated in North Korea for its brutality when it colonized the Korean Peninsula from 1910 to 1945.

Seiichi Ogawa, a senior researcher at the National Institute for Defense Studies and an expert on missiles and nuclear issues, says he supports the missile shield for Japan.

He says the plan reflects Japan's growing concerns over North Korea. He adds that, even if Japan does not build the system, North Korea is likely to continue to threaten it by developing and launching ballistic missiles.

Japanese anxiety over North Korea's missiles goes back to 1998, when Pyongyang test-fired a ballistic missile over Japan that landed in the ocean, to the surprise of many defense experts.

Soon after, Tokyo began joint research with Washington on missile defense, and started work on its own system of spy satellites. It launched two of them in March. The Defense Ministry's blueprint for a missile shield takes the new strategy further.

Prime Minister Junichiro Koizumi is working to set the legal foundations for deploying the system, by lobbying to amend Japan's pacifist Constitution, which renounces the use of force in settling international conflicts.

But this worries Japan's Asian neighbors, which were victims of Japanese militarism in the first half of the 20th century. If Japan is to beef up its military capabilities, then it could set off a new arms race in the region.

But Mr. Gatling, the aerospace consultant, plays down the problem, stressing that the system being contemplated is strictly defense.

"There is obviously concern among Japanese neighbors of the possibility of a more active Japan as it looks outside its borders," he said. "I do not think that this system in and of itself really presages that. I believe it is a natural evolution of their self-defense posture. The systems are only of utility, if someone fires a missile at Japan."