Iran said today it is considering plans to start building two new uranium enrichment plants from March, with the sites concealed in the mountains to avert air strikes. The announcement from Iran's atomic chief Ali Akbar Salehi came soon after top US General David Petraeus warned that Washington would now pursue pressure track against Iran to thwart its galloping nuclear programme. Salehi said, the enrichment capacities of the new sites would be similar to the existing facility in the central city of Natanz, where Tehran is refining uranium despite three sets of UN sanctions. According to the latest UN nuclear watchdog report, Iran has installed in Natanz 8,610 centrifuges, the device which rotates at supersonic speed to enrich uranium.Of these, 3,772 centrifuges are actively enriching uranium under the supervision of the International Atomic Energy Agency, IAEA. Iranian officials maintain Natanz has an annual capacity to produce about 30 tonnes of enriched uranium. According toIAEA, the Islamic republic currently has an estimated 2,065 kilogrammes of low-enriched uranium.