New York: The president of the UN conference drafting what could be the first-ever treaty to ban nuclear weapons says more than 120 countries have agreed on the text, which is expected to be formally adopted on Friday, US time, although all nuclear-armed nations are boycotting the effort.

Elayne Whyte Gomez, Costa Rica's ambassador to the UN in Geneva, said at a news conference on Thursday that "this will be a historic moment and it will be the first multilateral nuclear disarmament treaty to be concluded in more than 20 years."

In December, UN member states overwhelmingly approved a resolution calling for negotiations on a treaty that would outlaw nuclear weapons over strong opposition from nuclear-armed countries and their allies, which have boycotted the negotiations.

Whyte Gomez said 129 countries signed up to take part in negotiating the treaty, which represents two-thirds of the UN's 193 member states. But all nuclear states and NATO members have avoided the negotiations except for the Netherlands, which has US nuclear weapons on its territory and was urged by its parliament to send a delegation to the talks.

Australia took a lone stand as the only country in its neighbourhood to boycott the negotiations. At the time, Labor has described the government's decision not to participate in the drafting of the treaty as "astonishing".

Following Wednesday's final review of the text after nearly three weeks of negotiations, Whyte Gomez said she is "convinced that we have achieved a general agreement on a robust and comprehensive prohibition on nuclear weapons."

"We are on the verge of adopting the treaty on the prohibition of nuclear weapons," she said.

"I am really confident that the final draft has captured the aspirations of the overwhelming majority of those participating in the conference, including civil society."

Whyte Gomez said she hopes the treaty will be adopted by consensus, but she said the rules of procedure for the conference also allow for a vote.

The final draft treaty requires all countries that ratify "never under any circumstances to develop, test, produce, manufacture, otherwise acquire, possess or stockpile nuclear weapons or other nuclear explosive devices". It also bans any transfer or use of nuclear weapons or nuclear explosive devices - and the threat to use such weapons.

Not one of the nine countries believed to possess nuclear weapons - the United States, Russia, Britain, China, France, India, Pakistan, North Korea and Israel - is supporting a treaty.

Instead of adopting a total ban, the United States and other nuclear powers want to strengthen and reaffirm the nearly half-century-old Nuclear Non-proliferation Treaty, considered the cornerstone of global non-proliferation efforts.

That pact sought to prevent the spread of atomic arms beyond the five original weapons powers - the US, Russia, Britain, France and China. It requires non-nuclear signatory nations to not pursue nuclear weapons in exchange for a commitment by the five nuclear powers to move toward nuclear disarmament and to guarantee non-nuclear states access to peaceful nuclear technology for producing power.

North Korea's nuclear and ballistic missile tests, including its July 3 launch, have become a timely argument for proponents and opponents of the treaty ban.

AP