VIENNA —Attempts to find Arab-Israeli common ground on banning weapons of mass destruction from the Mideast have failed, and high-profile talks on the issue have been called off, diplomats said Saturday.

The two diplomats said the United States, one of the organizers, would likely make a formal announcement soon saying that with tensions in the region remaining high, “time is not opportune” for such a gathering. The diplomats spoke on condition of anonymity because they were not authorized to divulge the cancellation ahead of the formal announcement.

The meeting — to be held in Helsinki, Finland, by year’s end — was on shaky ground since it was agreed to in 2010 by the 189 member nations of the Nuclear Nonproliferation Treaty. Its key sponsors were the U.S., Russia and Britain, but they said such as meeting was only possible if all countries — especially Israel — agreed to attend.

The decision to postpone, if not to scrap it, will cast doubt on the significance of the NPT and its attempts every five years to advance nonproliferation. Any new attempt is unlikely until the NPT conference meets again in 2015.

Hopes for such a meeting were alive as recently as Tuesday, when Iran joined Arab nations in saying that it planned to attend, leaving Israel as the only undecided country. Tehran’s announcement came at a Brussels seminar on a Mideast nuclear-free zone also attended by Israel and the Arab countries and described as largely free of regional tensions. But the two diplomats said the decision to call off the Helsinki meeting had already been made by the time Iran declared Tuesday that it would attend.

But a decision to give up on staging such a gathering after it was approved by the NPT is more than a reflection of Mideast realities. It also is bound to weaken efforts at future NPT conferences to reconcile clashing visions of disarmament and nonproliferation efforts.

Daryl Kimball, head of Washington’s Arms Control Association, warned that “an indefinite cancellation of the long-awaited conference on a Middle Eastern WMD-free zone will only worsen the proliferation risks in the future and undermine the nuclear Nonproliferation Treaty.”