TOKYO >> A contentious debate over nuclear power in Japan is also bringing another question out of the shadows: Should Japan keep open the possibility of making nuclear weapons — even if only as an option?

It may seem surprising in the only country ever devastated by atomic bombs, particularly as it marks the 67th anniversary of the bombings of Hiroshima on Aug. 6 and Nagasaki three days later. The Japanese government officially renounces nuclear weapons, and the vast majority of citizens oppose them.

But as Japan weighs whether to phase out nuclear power, some conservatives, including some influential politicians and thinkers, are becoming more vocal about their belief that Japan should have at least the ability to make nuclear weapons.

The two issues are intertwined because nuclear plants can develop the technology and produce the fuel needed for weaponry, as highlighted by concerns that nuclear power programs in Iran and North Korea are masking bomb development.

"Having nuclear plants shows to other nations that Japan can make nuclear weapons," former Defense Minister Shigeru Ishiba, now an opposition lawmaker, told The Associated Press.

Ishiba stressed that Japan isn’t about to make nuclear weapons. But, he said, with nearby North Korea suspected of working on them, Japan needs to assert itself and say it can also make them — but is choosing not to.

Such views make opponents of nuclear weapons nervous.

"A group is starting to take a stand to assert the significance of nuclear plants as military technology, a view that had been submerged below the surface until now," says "Fukushima Project," a book by several experts with anti-nuclear leanings.

Adding to their jitters, parliament amended the 1955 Atomic Energy Basic Law in June, adding "national security" to people’s health and wealth as reasons for Japan’s use of the technology.

"The recognition that both nuclear issues must be addressed is heightening in Japan," said Hitoshi Yoshioka, professor of social and cultural studies at Kyushu University. The link between the two is "becoming increasingly clear."

Yoshioka sits on a government panel investigating the nuclear disaster spawned by the March 11 tsunami last year. The subsequent meltdowns at the Fukushima Dai-ichi plant have called into question the future of nuclear power in Japan, in turn raising concern among some bomb advocates.

Most proponents don’t say, at least not publicly, that Japan should have nuclear weapons. Rather, they argue that just the ability to make them acts as a deterrent and gives Japan more diplomatic clout.

The issue dates back to the 1960s. Historical documents released in the past two years show that the idea of a nuclear-armed Japan was long talked about behind-the-scenes, despite repeated denials by the government.

The papers were obtained by Japanese public broadcaster NHK in 2010 and more recently by The Associated Press under a public records request.

In a once-classified 1966 document, the government outlined how the threat of China going nuclear made it necessary for Japan to consider it too, though it concluded that the U.S. nuclear umbrella made doing so unnecessary at the time.

In meeting minutes from 1964, 1966 and 1967, Japanese officials weigh the pros and cons of signing the nuclear non-proliferation treaty, which would mean foregoing the nuclear option. Japan signed the treaty in 1970.

The government denials continued, even after former Prime Minister Yasuhiro Nakasone wrote in his 2004 memoirs that, as defense chief, he had ordered a secret study of Japan’s nuclear arms capability in 1970. The study concluded it would take five years to develop nuclear weapons, but Nakasone said he decided they weren’t needed, again because of U.S. protection.

In 2010, the Democratic Party of Japan, after breaking the Liberal Democratic Party’s half-century grip on power, reversed past denials and acknowledged the discussions had taken place.

Given the secretive past, former diplomat Tetsuya Endo and others are suspicious about the June amendment adding "national security" to the atomic energy law.

Backers of the amendment say it refers to protecting nuclear plants from terrorists. Opponents ask why the words aren’t then "nuclear security," instead of "national security."

Japan has 45 tons of separated plutonium, enough for several Nagasaki-type bombs. Its overall plutonium stockpile of more than 150 tons is one of the world’s largest, although much smaller than those of the U.S., Russia or Great Britain.

Tokyo Gov. Shintaro Ishihara, an outspoken conservative, has repeatedly said Japan should flaunt the bomb option to gain diplomatic clout. Former Prime Minister Shinzo Abe has expressed similar sentiments, although in more subdued terms.

The Yomiuri, the nation’s largest newspaper, made a rare mention of the link between nuclear energy and the bomb in an editorial defending nuclear power last year, saying that Japan’s plutonium stockpile "works diplomatically as a nuclear deterrent."

That kind of talk worries Tatsujiro Suzuki, vice chairman at the Japan Atomic Energy Commission, a government panel that shapes nuclear policy. Himself an opponent of proliferation, he said that having the bomb is a decades-old ambition for some politicians and bureaucrats.

"If people keep saying (nuclear energy) is for having nuclear weapons capability, that is not good," Suzuki said. "It’s not wise. Technically it may be true, but it sends a very bad message to the international community."