Two diplomats on Thursday said that Iran's national car company has made plans to purchase large quantities of carbon fiber, which is under UN embargo because it could be used in the country's nuclear program. The automaker's chief executive denied the allegation. The two diplomats independently told The Associated Press that their countries' intelligence agencies had gathered information that Iran Khodro executives were planning international orders for carbon fiber. Some would be used for fuel tanks in a new car that runs partly on compressed natural gas, the diplomats said. But carbon fiber is also a component of advanced centrifuges used to enrich uranium. Iran is enriching uranium that it says it wants only as nuclear fuel. The US and others fear it could be used in nuclear weapons. The two diplomats from International Atomic Energy Agency member nations said their intelligence agencies had reported suspicions that Iran wanted carbon fiber at least partly for its nuclear program. They spoke on condition of anonymity because their information was confidential. One of the diplomats told the AP that since early 2009, Iran Khodro has been taking steps for "a massive-scale procurement of carbon fiber." Iran Khodro head Manouchehr Manteqi, acting on orders of Iran's Supreme National Security Council, has "instructed a limited number of senior company executives to make the procurement as soon as possible," the diplomat said. The second diplomat told the AP that his country's intelligence services also believed Iran Khodro officials were preparing to make orders for carbon fiber. Manteqi vehemently denied that. "Reports that we are after carbon fiber are wrong," he told reporters in Teheran Wednesday, responding to a question from the AP. Iran's Supreme National Security Council oversees the country's nuclear program. It would be unusual for it to be involved in routine industrial production like car manufacture. Iran Khodro officials said last month that their new Soren ELX sedan would use a hybrid engine that could run on diesel and natural gas. They offered no details of the materials it would use. Carbon fiber is extremely strong, light and flexible and very difficult to make, requiring a level of expertise that experts say Iran does not possess. Alf Mischlich, an expert on hybrids with the German automaker Adam Opel GmbH, said cars powered by natural gas have tanks made either of reinforced steel or lighter, more rugged carbon fiber "but the tendency for new models is carbon-fiber." Toyota's prototype Camry Hybrid, for instance, has twin compressed natural-gas tanks with a carbon fiber-wrapped exterior shell. Iran has also used carbon fiber in the rotors of new, advanced centrifuges known as the IR-2, IR-3 and IR-4, which spin uranium gas to produce enriched uranium. Low-enriched uranium can be used as nuclear fuel. Much more enriched, it can be used in a warhead. The IR-2, IR-3 and IR-4 run two to three times faster than Iran's 1970s-vintage P-1 centrifuge, which uses aluminum rotors. The new models are also more robust than the P-1, which is prone to frequent breakdowns, say experts and IAEA officials. Iran has not said where it got the carbon fiber used in the IR-2, IR-3 and IR-4. It has displayed only a few finished models, a possible indication that it lacks carbon fiber and other materials under UN embargo. Because the UN prohibits sales of carbon fiber to Iran for any purpose, any purchases by Teheran would have to be through middlemen instead of directly from US, European or Asian manufacturers. Carbon fiber comes in a variety of strengths and thickness for applications ranging from manufacturing aerospace components to tennis rackets and even cellos, meaning not all forms are interchangeable. But Zsolt Rumy, the head of Zoltek, a carbon fiber manufacturer headquartered in Bridgeton, Missouri, said that in the case of natural gas tanks and centrifuge rotors, the specifications can overlap. "There is no reason why the same kind of carbon fiber cannot be used for both," he said.