The U.N. nuclear watchdog is concerned that Iran may now be working to develop a nuclear payload for a missile, the agency said in a confidential report today obtained by Reuters. The International Atomic Energy Agency report also confirmed Iran had produced its first, small batch of uranium enriched to a higher level -- 20 percent -- but said the Islamic Republic had failed to give inspectors the required advance notice. Both developments will stoke Western concerns that Iran is secretly bent on developing nuclear weapons capacity from the enrichment process. Tehran says the effort is meant only to yield electricity or radio-isotopes for agriculture or medicine. The IAEA has been investigating for five years Western intelligence reports indicating Iran has coordinated efforts to process uranium, test explosives at high altitude and revamp a ballistic missile cone in a way suitable for a nuclear warhead. In 2007 Washington issued an assessment saying Iran had halted such research in 2003 and probably had not resumed it. But its key Western allies believe Iran continued the programme -- and the IAEA report offered independent support for that perception for the first time. "The information available to the agency is extensive ... broadly consistent and credible in terms of the technical detail, the time frame in which the activities were conducted and the people and organisations involved," the report said. "Altogether this raises concerns about the possible existence in Iran of past or current undisclosed activities related to the development of a nuclear payload for a missile." As the passage of time made it more difficult to unearth relevant information, the IAEA said it was vital for Iran to cooperate with IAEA investigators "without further delay".