The United Nations adopted the treaty in July, though none of the nine countries that have nuclear weapons took part in shaping it or voting on it, and three of them -- NATO members Britain, France and the United States -- immediately said they had no intention of joining it.
NATO said the treaty "disregards the realities of the increasingly challenging international security environment" in the face of growing threats, particularly from Pyongyang, which recently carried out its sixth nuclear test and most powerful to date.
It added: "Seeking to ban nuclear weapons through a treaty that will not engage any state actually possessing nuclear weapons will not be effective, will not reduce nuclear arsenals, and will neither enhance any country's security, nor international peace and stability.
"Indeed it risks doing the opposite by creating divisions and divergences at a time when a unified approach to proliferation and security threats is required more than ever."
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Disarmament campaigners hailed the treaty as an important step but most NATO members boycotted the talks to prepare the text, as did Japan -- the only country to have suffered nuclear attacks, in 1945.
Nuclear powers argue their arsenals serve as a deterrent and say they remain committed to the gradual approach to disarmament outlined in the nuclear Non-Proliferation Treaty (NPT).