"Today's announcement does not change the US position on the treaty: the United States does not support and will not sign the 'Treaty on the Prohibition of Nuclear Weapons,'" a State Department spokesman told AFP.
"This treaty will not make the world more peaceful, will not result in the elimination of a single nuclear weapon, and will not enhance any state's security," the spokesman added, stressing that none of the world's nuclear-armed powers had backed the text.
The International Campaign to Abolish Nuclear Weapons (ICAN), which the Nobel committee rewarded for its efforts to consign the atomic bomb to history, was a key player in the treaty's adoption by 122 countries at the UN in July.
The accord was largely symbolic because none of the nine countries known or suspected of having nuclear weapons -- the United States, Russia, Britain, France, China, India, Pakistan, Israel and North Korea -- put their names down.
The State Department spokesman added that Washington remains committed to its obligations under the Nuclear Non-Proliferation Treaty and to working to "improve the international security environment, prevent and counter proliferation, and reduce nuclear dangers worldwide."
"We urge states to work with us on pragmatic, effective measures to accomplish this," he added.