TEHRAN (AFP) - Iran has so far produced five kilograms of 20 percent enriched uranium, atomic chief Ali Akbar Salehi said Wednesday, in defiance of world powers who want Tehran to end the controversial nuclear work. Iran began enriching uranium to 20 percent from February 9 following an order from President Mahmoud Ahmadinejad to Salehi. So far we have produced five kilos, Salehi told the ISNA news agency, adding that Iran needed one-and-half kilos of 20 percent enriched fuel every month to power the Tehran research reactor. Ahmadinejad had issued the order to begin the 20 percent enrichment work after a UN-drafted deal for world powers to supply fuel to the Tehran reactor hit a deadlock. Meanwhile, President Ahmadinejad urged Barack Obama to follow Tehrans example in fighting terrorism in a letter sent to his US counterpart, the Iranian leaders office said on Wednesday. Questions like the attack on Afghanistan, the expansion of instability and insecurity in the region and Americas backing for terrorism were raised in the letter, said Esfandiar Rahim Mashaie, the Iranian presidencys chief of staff. The president has also asked Obama to learn from Iran on how to combat terrorism, Mashaie said. In the letter, which was sent in the Iranian month of Esfand (February 20 to March 21), Ahmadinejad also brought up the topic of Sunni militant Abdolmalek Rigi, whom Iran arrested in February and accuses of being backed by Washington. The aim of writing this letter is for the world to grasp the view of the Islamic republic of Iran and also criticise US policies in the region, Mashaie said. Ahmadinejad had previously written a letter to Obamas predecessor George W Bush in May 2006. The same year in November he had also written an open letter to the American people. In recent days, Ahmadinejad has raised fresh doubts over the occurrence of the 2001 attacks on the United States, and even written to the UN chief Ban Ki-moon to launch a probe into what he has called a big lie.