Japan's constitution allows it to possess nuclear weapons as long as they are kept to a minimum level necessary for self-defence, although the country has no intention of holding such arms, the government said in a statement on Tuesday.
The statement, written in response to a question from an independent lawmaker, comes amid controversy over whether the country should debate holding nuclear arms -- an emotive issue in the only nation to have suffered nuclear attacks.
"From a purely legal standpoint, even Article Nine of the constitution does not bar our country from possessing minimum capabilities necessary for self-defence," the statement said, repeating a position the government has made clear in past parliamentary debate.
"Even with nuclear weapons, we've understood that possessing them would not necessarily violate the constitution as long as it is kept within such limits," it said.
But the statement said Japan would stick to its self-imposed "three non-nuclear principles" banning the possession, production and import of nuclear arms and that the government had no plans to debate a change in that stance.
It also said that Japan's basic law on atomic energy limits research, development and use of such power to peaceful purposes, while the country is bound under the nuclear Non-Proliferation Treaty not to receive or manufacture nuclear weapons.
Controversy over debate on nuclear arms erupted last month when Shoichi Nakagawa, the policy chief of the ruling Liberal Democratic Party, said Japan should discuss if it should acquire nuclear weapons after North Korea conducted a nuclear test.
The foreign minister has also said debate should not be ruled out, prompting opposition lawmakers to call for his resignation.
Prime Minister Shinzo Abe has said repeatedly that Japan would maintain its decades-old ban on nuclear weapons, denying that the government would even discuss the topic.
Article Nine of Japan's US-drafted 1947 constitution renounces the right to go to war and prohibits the maintenance of a military, although it has been interpreted as allowing armed forces for purely defence purposes.
Analysts say Japan is capable of producing nuclear weapons with its high technology and a stockpile of plutonium from its nuclear power plants, but they add that it is highly unlikely to do so, given opposition both at home and abroad.