A four-week U.N. review conference on the Nuclear Non-Proliferation Treaty ended Friday without adopting a consensus document after negotiators failed to narrow differences over a proposal to make the Middle East a nuclear weapons-free zone.

The failure to produce an outline for actions for the next five years at the meeting, which took place in the 70th anniversary year of the atomic bombings of Hiroshima and Nagasaki, raised concerns that efforts to advance toward a world free of nuclear arms will lose momentum.

The conference president, Algerian diplomat Taous Feroukhi, admitted to a lack of consensus at a plenary meeting that was held after hours of delay. Citing "diverging expectations of state parties for a progressive outcome," she said "it would be impossible for any single consensual document to possibly meet the highest aspirations of all parties."