TEHRAN (Reuters/AFP) - Iran will start producing 20 per cent enriched nuclear fuel from tomorrow (Tuesday) at the Natanz plant, the head of its Atomic Energy Organisation was quoted as saying. We will inform the IAEA in a letter tomorrow (Monday) of our intention to enrich uranium to 20 per cent, Ali Akbar Salehi told the Arabic-language Al-Alam television, referring to the International Atomic Energy Agency. The higher enrichment will begin at the Natanz plant from the day after tomorrow (Tuesday), he added. Natanz is in the central province of Isfahan. Earlier, Iranian President Mahmoud Ahmadinejad ordered Salehi to enrich uranium to 20pc, in a fresh challenge to world powers days after appearing to accept a UN-drafted nuclear fuel deal. Ahmadinejad also blamed the world powers for the stalemate over the fuel deal, but left the door open for possible negotiations over the proposal. I had said let us give them (world powers) two to three months and if they dont agree, we would start ourselves, Ahmadinejad said in a speech at an exhibition on laser technology which was broadcast live on state television. Now Dr (Ali Akbar) Salehi, start to make the 20pc with the centrifuges, he told the atomic chief, who was sitting in the audience. Ahmadinejad insisted that world powers 'unconditionally accept exchanging Irans low-enriched uranium (LEU) for high purity 20pc enriched uranium to be used as nuclear fuel for the Tehran reactor which makes medical isotopes. He also said that Iran now had laser technology which can enrich uranium to any level but Tehran would resort to using centrifuges - the device which rotates at supersonic speed - for processing high purity uranium. Ahmadinejads statement comes after he indicated in an interview on state television last Tuesday that Iran was ready to send its LEU abroad for conversion into 20 percent nuclear fuel. ILNA news agency reported that Foreign Ministry spokesman Ramin Mehmanparast said that enriching uranium to 20 per cent was Irans 'right and not in contradiction to the NPT (Non Proliferation Treaty) to which Tehran is a signatory. Defending the plan, Mehmanparast said that Iran will need vast amount of nuclear fuel in future which will be partly met by in-house production and partly from imports if those who make it cooperate. Ahmadinejad said Sunday that if the world powers come forward and say 'we will exchange (uranium) unconditionally and cooperate on your reactors and medicine... fine then we will cooperate too. He laid the blame for the fuel deadlock entirely at the door of world powers. Recently we said lets swap (uranium) though we can produce the 20 per cent, but they started playing games, he said. They have just sent messages though that they want to fix things. The road to engagement is open. We did not block it. Salehi himself said that the world powers had little time left for entering into the fuel deal with Iran. If they do not enter this fuel exchange we have to be ready for 20pc enrichment, Fars quoted him as saying. He said Iran had 'received messages for the exchange and there was 'optimism in talks... but not much time was left for the world powers.