Australia is following nearly 40 countries, including the US, Britain and France, and not taking part in talks on a nuclear weapons ban treaty starting at the United Nations.
US Ambassador Nikki Haley told reporters on Monday the countries skipping the negotiations are instead committed to the Non-Proliferation Treaty, which entered into force in 1970 and is aimed at preventing the spread of nuclear weapons and weapons technology.
"There is nothing I want more for my family than a world with no nuclear weapons. But we have to be realistic. Is there anyone that believes that North Korea would agree to a ban on nuclear weapons?" Haley told reporters.
The United Nations General Assembly adopted a resolution in December - 113 in favour to 35 against, which included Australia, with 13 abstentions - that decided to "negotiate a legally binding instrument to prohibit nuclear weapons, leading towards their total elimination" and encouraged all member states to participate.
In February this year an Australian foreign affairs department spokeswoman told Guardian Australia that it would not be participating in the treaty to ban nuclear weapons, as it is committed to non-proliferation.
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The Trump administration is reviewing whether it will reaffirm the goal of a world without nuclear weapons, a White House aide said last week, referring to an aim embraced by previous Republican and Democratic presidents and required by a key arms control treaty.
Britain's UN Ambassador Matthew Rycroft said: "The UK is not attending the negotiations on a treaty to prohibit nuclear weapons because we do not believe that those negotiations will lead to effective progress on global nuclear disarmament."
Deputy French UN Ambassador Alexis Lamek said the security conditions were not right for a nuclear weapons ban treaty.
