Iran is closer today than ever before to obtaining the necessary enriched uranium for a nuclear bomb, Prime Minister Binyamin Netanyahu said on Thursday evening.He was reacting to the publication of details of a confidential report by the International Atomic Energy Agency that Iran had begun installing advanced centrifuges at its main uranium enrichment plant.Such machines could enable Iran to significantly speed up its accumulation of material that could be used to make a nuclear weapon.It was not clear how many of the new centrifuges Iran aims to install at Natanz, which is designed for tens of thousands.An IAEA note informing member states late last month about Iran’s plans implied that it could be up to 3,000 or so.Iran has for years been trying to develop centrifuges more efficient than the erratic 1970s IR-1 model it now uses, but their introduction for full-scale production has been dogged by delays and technical hurdles, experts and diplomats say.Iran has also started testing two new centrifuge models, the IR-6 and IR6s, at a research and development facility, the IAEA report said. Centrifuges spin at supersonic speed to increase the ratio of the fissile isotope in uranium.Iran’s defiance is likely to anger world powers ahead of a resumption of talks with Tehran next week. Six world powers and Iran are due to meet for the first time in eight months in Kazakhstan on Tuesday to try again to break the impasse, but analysts expect no real progress toward defusing suspicions that Iran is seeking nuclear weapons capability.US State Department spokeswoman Victoria Nuland said in Washington Thursday that Iran's installation of new-generation centrifuges would be "yet another provocative step." White House spokesman Jay Carney warned Iran that it would face further pressure and isolation if it fails to address international concerns about its nuclear program in the Feb. 26 talks with world powers in the Kazakh city of Almaty.In a more encouraging sign for the powers, however, the IAEA report said Iran in December resumed converting some of its uranium refined to a fissile concentration of 20 percent to powder for the production of reactor fuel.That helped restrain the growth of Iran’s higher-grade uranium stockpile since the previous report in November, a development that could buy more time for diplomacy and delay possible Israeli military action.The report said Iran had increased to 167 kg. its stockpile of 20-percent uranium – a level it says it needs to make fuel for a Tehran research reactor but which also takes it much closer to weapons-grade material, which could be obtained if it were processed further.Netanyahu termed the report “very grave,” and said it proved that Iran was moving swiftly toward the red line he had set out at the United Nations in September. He said during that address that Iran must be stopped before it crossed the line, something he said at the time could happen as early as the spring.The Prime Minister’s Office said that preventing Iran from obtaining nuclear weapons would be the first issue on the agenda when US President Barack Obama came to visit in less than a month’s time.According to the report, 180 so-called IR-2m centrifuges and empty centrifuge casings had been hooked up at the plant near the central town of Natanz. They were not yet operating.