Iran said last week that it had completed its first batch of 20 percent enriched uranium and will soon triple production. Uranium enriched to 20 percent can set off a nuclear reaction, scientists say, but is not weapons grade.Answering a question from CNN, Ahmadinejad said it was not economical for Iran to perform its own enrichment The Islamic republic would rather buy it from other sources, he said But the nation's supply of enriched uranium was running low and Iran could not afford to wait any longer, Ahmadinejad said.