United Nations (United States) (AFP) - The failure of the world's nuclear powers to make headway on disarmament is threatening to unravel a landmark treaty coming up for review next week, the UN's disarmament chief warned Wednesday.

The 190 countries that have signed the Non-Proliferation Treaty (NPT) are opening a month-long conference on Monday at the United Nations to take stock amid much gloom over the lack of progress.

"We have a stalling in the path to a nuclear-free world," said Angela Kane, the UN high representative for disarmament affairs.

"The nuclear-weapons states are not living up to their side of the bargain," Kane told a meeting organized by the International Peace Institute.

Reached in 1968, the NPT has been billed as a grand bargain between the five nuclear powers -- Britain, China, France, Russia and the United States - and non-nuclear states which agreed to give up atomic weapon ambitions in exchange for disarmament pledges.

But 45 years after the NPT entered into force, non-nuclear states are feeling increasingly frustrated about the outcome.

"Right now, the non-nuclear states need to be given the sense that they are taken seriously," said Kane.

Delegates to the NPT conference are working on a document laying out priorities on the disarmament agenda for the next five years, but some diplomats have not ruled out that disagreements could lead to a collapse of the conference.

Kane warned that the next five years will be crucial to ensure that the NPT "retains credibility."

She suggested that there be a roadmap with targets that are "not far off in Never-Never-Land" to reassure non-nuclear states that they have signed on to a treaty that is "worthwhile."

Frustration over the slow pace of disarmament has focussed on the United States and Russia which have made little effort on cutting their nuclear arsenals since 2011.

A proposed nuclear weapons-free zone for the Middle East has failed to materialize despite a plan agreed at the last NPT conference to begin talks on the proposal in 2012.

On a brighter note, Kane welcomed the framework nuclear deal reached for Iran and said it could "give pause" to the nuclear threshold states that have yet to join the NPT: Israel, Pakistan and India.