February 18, 2010 3:07 p.m. EST
(CNN) -- Iran may currently be working on secretly developing a nuclear warhead for a missile, the IAEA director general said Thursday in a draft report.
It's the first time that the United Nations' nuclear watchdog agency has issued such a strong warning about current Iranian nuclear activities.
The statement comes in a draft report obtained by CNN. The report, dated Thursday, has not yet been approved by the board of governors of the International Atomic Energy Agency.
The report also said Tehran began enriching uranium to a level at which it can sustain a nuclear reaction before United Nations inspectors arrived to monitor the process, and in defiance of a specific request that it not so do.
The IAEA asked Iran earlier this month not to boost uranium enrichment to 20 percent "before the necessary additional safeguards procedures were in place."
When inspectors arrived the following day, February 10, "they were informed that Iran had already begun to feed the low enriched" uranium into the enrichment machinery "the previous evening."
The United States and its allies have long feared that Iran aims to develop the capacity to build a nuclear bomb. Iran denies it, saying its nuclear program is designed to produce civilian energy and for medical use.