VIENNA Iran is testing an advanced centrifuge at its Natanz nuclear complex, diplomats said on Wednesday, a move that could lead to Tehran enriching uranium much faster and gaining the means to build atom bombs.
Iran says it wants nuclear energy only for electricity so it can export more oil. But it is under sanctions for hiding the program until 2003, preventing U.N. inspectors since then from verifying it is wholly peaceful and refusing to suspend it.
Tehran's quest to produce usable amounts of nuclear fuel has been hampered by problems getting a 1970s vintage of centrifuge, the "P-1", to run nonstop at maximum speed. Iran had 3,000 P-1s working by November, a basis for launching industrial-scale enrichment, but only at an estimated 10 percent of capacity.
But diplomats tracking Iran's dossier said it had started mechanical tests, without nuclear material inside, of a more durable, efficient model in the pilot wing of the Natanz plant.
"The Iranians have begun to run in the advanced model. It's not yet known what stage the testing has reached or exactly how many there are, although it appears to be several dozen," said a Western diplomat with access to intelligence.
A senior diplomat familiar with the International Atomic Energy Agency's file on Iran confirmed it recently began testing centrifuges based on a "P-2" design, used more recently in the West and able to enrich uranium 2-3 times as fast as the P-1.
He declined to elaborate, saying details would come in a report IAEA Director Mohamed ElBaradei will deliver to the Vienna-based agency's 35-nation Board of Governors and the U.N. Security Council later this month.
It was not known how successful the "dry runs" with the new machines had been or when they might be test-fed with uranium gas for enrichment. Iran had no immediate comment.
But diplomats and analysts said Iran had decided to install no more of the antiquated P-1s in Natanz's main, underground production hall and expand capacity instead only with their more efficient successor.
"On the positive side, (shifting advanced centrifuge activity) to the pilot plant at Natanz would bring the program under more international scrutiny (through IAEA inspections)," said David Albright, a physicist and non-proliferation expert.
"On balance, though, I believe this is a disturbing development. Iran appears to have made progress in secret on the P-2 and may now be close to enriching uranium with it," said Albright, head of the Washington-based Institute for Science and International Security and an ex-U.N. weapons inspector.
Iran first revealed in 2006 that it was developing supposedly state-of-the-art centrifuges at workshops put off-limits to IAEA inspectors in retaliation for steps by Western powers to impose initial sanctions on Tehran.
The IAEA got a first, one-off look at the advanced centrifuge effort when Iran allowed ElBaradei to visit a workshop in Tehran last month in a gesture of transparency, diplomats versed in the Iran file said.
This was no breakthrough in Western eyes. Diplomats said Iran could not defuse mistrust in its nuclear agenda unless it accepted a binding regime of broader, snap inspections by agency professionals, and suspended enrichment-related activity.
ElBaradei has urged Iran to adopt the IAEA's Additional Protocol, which would allow far-ranging inspections to assess how close Iran may be to mastering enrichment technology and verify that it is not being turned to illicit military ends.
But Tehran has linked fuller cooperation with an end to sanctions, extending a frozen war of nerves with Western powers over which side should make what gesture first.
A U.S. intelligence report in December said Iran stopped actively trying to "weaponize" nuclear materials in 2003.
But it also said Iran has made technical progress towards refining uranium in amounts sufficient for a bomb in 2-7 years, if it decided to do so at sites not declared to inspectors.
ElBaradei's report is expected to say the IAEA is closer to wrapping up an inquiry into Iran's past nuclear activities.
But six world powers have drafted wider Security Council sanctions against Iran, saying clarifying old issues counts for less than Tehran's failure to open the books on its present program or shelve enrichment in return for trade benefits.
(Editing by Keith Weir)