Iran is operating a newer, more advanced centrifuge at the country's Pilot Fuel Enrichment Plant at Natanz, a State Department official who works on arms control and WMD issues has confirmed to FOX News.

U.S. officials were trying to determine the origin of the new centrifuges.

To enrich uranium to the high levels needed for a nuclear weapon, centrifuges are assembled in groups of 164 — known as "cascades."

Mastery of a single cascade is an extremely difficult process, but once that is achieved it is fairly easy for an industrialized country to attain a nuclear weapons capability because it requires only the building of more cascades and enough fissile uranium to feed into them.

Previously, Iran has been known to be operating P-1 centrifuges, a 1970s-era model; however, Iranian President Mahmoud Ahmadinejad has made some unverifiable boasts about experimentation with the P-2: The newer, faster model developed by Pakistan and sold on the black market to some rogue nations by the A.Q. Khan network.

"We're not certain that these are P-2s ... or a variant of it," the State Department official said.

The International Atomic Energy Agency, the U.N. nuclear watchdog, was expected to issue its latest report on the status of the Iranian nuclear program around Feb. 20, and will almost certainly provide more information about Iran's work with centrifuges.

Although the contents of the document have not been disclosed in advance, published reports and other evidence suggest that, in keeping with the custom of IAEA Director General Mohamed ElBaradei, it will be non-confrontational in tone and accentuate the positive aspects of Iran's behavior in the case.

German Foreign Minister Frank-Walter Steinmeier, a key player in the Western allies' diplomacy with Iran, told an interviewer Feb. 4 that IAEA will "perhaps ... publish a report in the next few days which portrays Iran's cooperation in clarifying the unresolved issues regarding the Iranian nuclear program in a rather more favorable light."

Such a report by ElBaradei would have the effect, like his past reports, of complicating U.S. efforts to rally the international community to take decisive action to halt Iran's uranium enrichment.

Steinmeier said he and his colleagues "no longer fear that they [the Iranians] will be so advanced by 2009." He added that the National Intelligence Estimate released by the director of National Intelligence in December, which claimed Tehran suspended work on nuclear warhead designs back in 2003, "has shown that we are no longer under quite so much time pressure."

James Rosen joined Fox News Channel (FNC) in 1999. He currently serves as the chief Washington correspondent and hosts the online show "The Foxhole." His latest book is "A Torch Kept Lit: Great Lives of the Twentieth Century" (Crown Forum, October 4, 2016).