David E. Sanger

WASHINGTON: International nuclear inspectors will soon report that Iran has installed hundreds of new centrifuges in recent months and may be speeding up production of nuclear fuel while negotiations with the United States and its allies have ground nearly to a halt, according to diplomats and experts briefed on the findings.

Almost all of the new equipment is being installed in a deep underground site on a military base considered virtually invulnerable to military attack.

The report will also indicate, according to the officials familiar with its contents, that Iran is increasingly focused on enriching uranium to a level of 20 percent — a purity that it says it needs for a specialty nuclear reactor that it insists is used only for medical purposes, but that outside experts say gets it most of the way to the level needed to produce a workable nuclear bomb.

The report does not attempt to address the question of whether Iran has made a decision to build a nuclear weapon; U.S. intelligence officials believe it has not, and Iran insists it wants to use nuclear power for peaceful ends.

It is unlikely that Iran has begun to use the new centrifuges to produce fuel, and even with significant increase in fuel production it would still take months, at the least, to produce a crude weapon. By most U.S. government estimates, Iran would need at least two years to develop a workable warhead that could fit atop a missile.

Nonetheless, the report by the International Atomic Energy Agency’s experts, first reported by Reuters, is likely to renew the debate over Iran’s intentions at a time when Israeli officials are stepping up their warnings that the window to conduct a pre-emptive military strike is closing.

A faction led by Israel’s defense minister, Ehud Barak will almost certainly argue that Iran has moved closer to what Barak calls a “zone of immunity,” a point at which so much equipment is installed in the underground facility that it will soon be too late for Israel to stop Iran from producing a weapon, should it choose to do so.

The critical question likely to be prompted by the IAEA report, which could be published as soon as Wednesday, comes down to this: How much closer is Iran to gaining a nuclear weapons “capability” — that is, the ability to produce a bomb on relatively short notice?