The chief UN nuclear inspector said Monday his agency cannot guarantee that Iran's nuclear program is peaceful, despite four years of investigations and that doubts will persist until Tehran decides to cooperate with his experts.

Mohamed ElBaradei, head of the International Atomic Energy Agency, spoke as board member nations of the IAEA gathered for a session on approving the suspension of dozens of technical aid programs to Iran as part of Security Council sanctions meant to punish Tehran for its nuclear defiance.

Although the issue is not expected to come up until Tuesday at the earliest, the focus of the International Atomic Energy Agency's 35-nation board meeting will be on Iran's refusal to suspend uranium enrichment activities and linked problems.

Ali Ashgar Soltanieh, Iran's chief delegate to the IAEA, said again his country would "never give up its inalienable right" to develop enrichment, which Tehran says it wants to develop to generate power but which also can produce the fissile material for nuclear warheads.

ElBaradei, whose agency has spent more than four years probing the nature of Tehran's nuclear activities, said the IAEA remains "unable to provide the required assurance about the peaceful nature of Iran's nuclear program."

In opening comments, he said that unless Tehran takes "the long overdue decision" to cooperate with the IAEA, it "will have no option but to reserve its judgment about Iran's nuclear program, and as a result the international community will continue to express concern."...