TOKYO North Korea's rocket launch has sparked calls for Japan to consider developing a pre-emptive strike capability, though any such plan could undermine regional stability and attract only lukewarm support from voters.
Tokyo did deploy naval and land-based ballistic missile defences over fears that part or all of the rocket North Korea launched over Japan on Sunday could have fallen on its territory.
But some argue Japan should go much further, despite limits imposed by its pacifist constitution.
"We should hold a proper debate about attacking launch bases and about shelters in case something does happen," Kyodo news agency reported former finance minister Shoichi Nakagawa as saying on Sunday.
North Korea said the rocket launched a satellite, but the U.S. military said no satellite had gone into orbit. Many countries saw Sunday's launch as a thinly disguised missile test.
North Korea's previous rocket launches have instigated talk of pre-emptive strikes before in Japan. Former defence minister Fukushiro Nukaga was among those who suggested an overseas strike capability should be discussed following a July 2006 launch.
"A lot of people have been pushing for it for awhile and see it as a plausible option," said Brad Glosserman of Hawaii-based think tank Pacific Forum CSIS. "Personally, I think it's extremely destabilising."
Talk in Japan in 2006 about acquiring an overseas strike capability infuriated South Korea, who called it "dangerous and reckless" and China, who accused Japan of "pouring oil on fire."
The Japanese public, which has exhibited a pacifist streak since the country's World War Two defeat, was unenthusiastic in 2006, with a majority saying in a media poll they did not feel Japan should be able to conduct pre-emptive attacks.
Japan's pacifist constitution has been interpreted as allowing a military only for self-defence and some experts say a pre-emptive strike doctrine would stretch that too far.
At present, Japan lacks the necessary missiles or long-range bombers, and acquiring them would be costly.
Given the ballooning national debt and rising spending to combat Japan's worst recession since World War Two, the political momentum may be lacking to transform the armed forces.
Japanese politics has been stalemated by a divided parliament -- the country has had three prime ministers in less than two years and an election is due by October.
"It is very hard to focus for very long and very hard, even on things as important as national security, given the economy," said Richard Samuels, a political science professor at Massachusetts Institute of Technology and an expert in Japan's security policy.
"Since the incident proceeded without direct impact on Japan, I think we are not going to get the hard focus we got in 1998."
That year's launch of a North Korean long-range missile over Japan prompted Tokyo to speed up deliberations and eventually sign up to the ballistic missile defence system it is now building in cooperation with the United States.
While many believe direct strikes on North Korea would be difficult to justify, beefing up the missile shield on which Japan has spent more than 66 billion yen (438.7 million pounds) over the past five years is a more acceptable option for some commentators.
"We cannot of course destroy their missiles in the territorial air space of North Korea," said foreign policy expert Yukio Okamoto, who favours more focus on a system to intercept at the rocket booster phase.
"We ought to have a more strategic defence system and a lot of research and development is needed for that," he said. "I think we should aim at that and I think there is a strong thrust towards that direction now."
Ruling Liberal Democratic Party (LDP) lawmaker and former defence minister Yoshimasa Hayashi agreed.
"There are two cases for pre-emptive strikes," he said. "One is before they launch, the other is the boost phase. Legally speaking, the boost phase could be easier than attacking the base even before they do anything."
The main difficulty in that case would be technical, with a laser strike from a satellite the most feasible option, he said.