The United States is still haunted by a nightmare of 2006, says an insider of the Defense Ministry. But the “nightmare” he refers to is not the first nuclear test by North Korea in October that year, but rather an internal report compiled by the Japanese government a month earlier on “the possibility of domestically producing nuclear weapons.” North Korea carried out its third nuclear test on Feb. 12, 2013.

The U.S. is nervous about Japan, according to the insider. It is not publicly known that the Foreign Ministry has been conducting studies clandestinely on potential development of nuclear arms.

Two days after the latest nuclear test by the North, U.S. President Barack Obama told Prime Minister Shinzo Abe in a telephone meeting that there would be no change whatsoever in America’s commitment to defend Japan, including nuclear deterrence through its nuclear umbrella over Japan.

Obama’s comment was meant not only to reconfirm the U.S.’s commitment to the Japan-U.S. Security Treaty but also to discourage Japan from following the path toward becoming a nuclear power.

According to Japanese and American diplomatic sources, Obama’s message to Abe came at the strong urging of the U.S. State Department following close consultation between diplomacy and defense officials of both countries.

In South Korea, possessing nuclear weapons has been openly debated in the parliament. But Japanese politicians and bureaucrats have traditionally avoided making any suggestion that Japan should arm itself with nuclear weapons.

A high-ranking Foreign Ministry official said that the crisis surrounding this country has “moved to a different stage” in the wake of North Korea’s latest long-range rocket firing and nuclear test.

The possibility of North Korea, a de facto nuclear power, acquiring capability to launch a nuclear attack on the U.S. mainland is growing. In this situation, Japanese diplomats are starting to be concerned: Will the U.S., whose people are exposed to a direct crisis, provide a nuclear umbrella to Japan and South Korea in case of a nuclear attack from North Korea on these countries?

In addition to ultra-hawkish politicians like former Tokyo Gov. Shintaro Ishihara and the late former Finance Minister Shoichi Nakagawa, who openly argued that Japan should have nuclear weapons, opinions favoring nuclear armament have also been expressed, officially and unofficially, by some of the politicians who served as prime minister, including Nobusuke Kishi (prime minister from 1957 to 1960), Hayato Ikeda (1960-64), Eisaku Sato (1964-72), Yasuo Fukuda (2007-08) and Taro Aso (2008-09).

A newspaper reporter assigned to the Foreign Ministry has attributed this attitude of these political leaders to “education” they have received from bureaucrats of the central government.

Another reporter of a major national newspaper recalled a meeting last September between then Prime Minister Yoshihiko Noda and U.S. Secretary of State Hillary Rodham Clinton, in which she urged him to rethink his plan to give a Cabinet endorsement to the policy of totally eliminating Japan’s nuclear power generation during the 2030s.

This reporter quoted a conservative Diet member of the Democratic Party of Japan as saying that a high-ranking Foreign Ministry official admitted not only that Clinton’s move apparently stemmed from the fear of losing benefits emanating from the bilateral Cooperation Agreement on Nuclear Energy but also that Japan should avoid a situation at any cost in which Japan will lose an option to possess nuclear weapons.

The aforementioned newspaper reporter assigned to the Foreign Ministry said that the ministry regards arming Japan with nuclear weapons as an important diplomatic card.

Obviously Japan cannot expect to arm itself with nuclear weapons overnight. Too much impurity is contained in plutonium 239 — an essential ingredient for a nuclear bomb that is formed as a result of the operation of commercial reactors in Japan — while the country’s uranium enrichment capability is not enough to make a nuclear bomb. The 2006 report says that it would take three to five years and ¥200 billion to ¥300 billion for Japan to possess nuclear weapons.

The report can be interpreted to mean that Japan has the potential capability to produce and possess nuclear weapons of its own. And it is the Foreign Ministry that wants to retain this potential, and its U.S. counterpart, the State Department, is worried about it. This means that the Foreign Ministry has something ulterior in view while dealing with the U.S., which is staunchly opposed to Japan’s developing or possessing nuclear arms and to its doing away with nuclear power generation.

The U.S. government is said to have informed the Japanese Defense Ministry in detail of a plan to strengthen its nuclear deterrence system in the wake of the February nuclear test by North Korea. Although no content of the plan has been known, Washington is believed to be reviewing the deployment of nuclear weapons in the Far East.

On the very day — Feb. 12 — of the North Korean nuclear test, two Russian strategic bombers flew near Guam, causing U.S. F-15 Eagle fighters to scramble. It is thought that this represents a move by Moscow, which has become keenly aware of the U.S.’s nuclear strategy.

In March, Thomas E. Donilon, national security adviser to President Obama, said that the U.S. will neither recognize North Korea as a nuclear power nor tolerate development of nuclear weapons by Pyongyang.

This determination by Washington absolutely not to accept an increase in the number of nuclear-armed countries is also directed at Japan.

This is an abridged translation of an article from the April issue of Sentaku, a monthly magazine covering Japanese political, social and economic scenes.