Iran is prepared to review the P5+1's fuel exchange proposal, Iranian Foreign Minister Foreign Minister Manouchehr Mottaki said in an interview with the Iranian news agency published Saturday. During the interview, Mottaki stated that Teheran recently offered to move nuclear fuel to the island of Kish, in the Persian Gulf. The proposal, he said, was a gesture of goodwill which "aimed to open a door for the other side." In recent weeks, US officials warned that the window of opportunity for talks with Iran was rapidly closing. Meanwhile on Saturday, the Fars news agency quoted Iranian nuclear chief Ali Akbar Salehi as saying that the Russian-built nuclear power plant in Bushehr would have to undergo only three more rounds of testing before becoming operational. "We have drawn up a timetable for the operation of the Bushehr plant with Russia and fortunately we are ahead of this timeframe," Salehi reportedly said. Iranian President Mahmoud Ahmadinejad on Friday night said that Teheran was prepared to reach a nuclear fuel agreement with the West if the US and Western powers stopped threatening the Islamic republic, the French News Agency reported. "Everything is possible ... but not in a climate where they threaten us. They have to change their vocabulary, in respect and legality," Ahmadinejad told AFP in an interview on the sidelines of the UN Climate Summit in Copenhagen. "In this case we will say, very good you want to keep your word, in this case we are ready to sit down at the table to reach an agreement," the Iranian premier was quoted as saying. Ahmadinejad's remarks came hours after Salehi said the country had started making more efficient centrifuge models that it plans to put into use by early 2011, a statement which underscored Teheran's defiance and adds to international concerns over its nuclear ambitions. Salehi said Iranian scientists were still testing the more advanced models before they become operational at the country's enrichment facilities. Teheran has been saying since April that it is building more advanced centrifuges capable of enriching uranium with higher efficiency and precision, but Salehi's remarks were the first indication of a timeline when the new models could become operational. The new centrifuge models will be able to enrich uranium much faster than the old ones; some experts estimate that this next generation could double or even triple the rate of uranium production. Such a development would add to growing concerns in the West because they would allow Teheran to accelerate the pace of its program. That would mean Iran could amass more material in a shorter space of time that could be turned into the fissile core of missiles, should Teheran choose to do so. Iran's uranium enrichment is a major concern to the international community, worried that the program masks efforts to make a nuclear weapon. Teheran insists its enrichment work is peaceful and only meant to generate electricity, not make an atomic bomb. Iran has threatened to expand its enrichment program tenfold, even while rejecting a plan brokered by the UN nuclear watchdog agency to supply fuel for Iran's research reactor if Teheran exports most of its enriched stockpile. The UN plan would leave Iran - at least temporarily - without enough uranium to produce a bomb. Centrifuges are machines used to enrich uranium - a technology that can produce fuel for power plants or materials for a nuclear weapon. Uranium enriched to low level is used to produce fuel but further enrichment makes it suitable for use in building nuclear arms. "We are currently producing a new generation of centrifuges named IR3 and IR4," Salehi told the semiofficial Fars news agency. "We hope to use them by early 2011 after resolving problems and defects." He did not elaborate on the technical details or the difference between various centrifuge types. However, Salehi added: "We are not in a rush to enter the industrial-scale production stage." The new centrifuges would likely replace the decades-old P-1 centrifuges, once acquired on the black market and in use at Iran's main uranium enrichment facility in Natanz, central Iran. Iran has said the new centrifuges would also be installed at Iran's recently revealed secret uranium enrichment facility. The plant is still under construction at Fordo, near the holy city of Qom. Salehi said that more than 6,000 centrifuges are currently enriching uranium - 2,000 more than the figure mentioned in a November report by the UN watchdog, the Vienna-based International Atomic Energy Agency. The IAEA has reported that it is watching Iran's efforts to improve its centrifuges. Iran says it will install more than 50,000 centrifuges at Natanz, but currently they have installed fewer than 9,000, so there could easily be room for more advanced models in the future, a Vienna nuclear expert said. The expert spoke on condition of anonymity because of the sensitivity of the issue. Iranian officials have claimed that most parts for the new centrifuges are made domestically and others have been imported - a sign that Iran was able to get around UN sanctions imposed on the country for its refusal to suspend uranium enrichment. Iran's defiance has not wavered amid recent signals of possible more UN sanctions over its enrichment. Salehi said Friday such new sanctions won't stop Iran from developing its nuclear program. "We don't welcome new [UN Security Council] resolutions," he told ISNA, another semiofficial news agency. "But resolutions won't stop us in any field, including the nuclear."