Asked about the likelihood of Iran conforming to the deadline set down by the IAEA on September 12, Mohamed ElBaradei told CNN: "I hope so, I hope at least that I will not be in a position to report that I am not getting the full cooperation and transparency from Iran."
"There is a degree of impatience on the part of the international community that this issue can not continue for ever. If not, I am afraid that the issue will escalate beyond the confines of the agency," he added.
However, he refused to speculate on the consequences of referring the matter to the UN Security Council, which could impose sanctions.
"I hope that the issue will not have to be brought to the Security Council. I hope that Iran will cooperate and take whatever corrective measures needed for us to be able to present a positive report," he added.
"They say their program is for peaceful purposes and if they really have nothing to hide it is to them to open all their facilities and all their books," he said.
The IAEA has given Iran until the end of next month to answer all its questions concerning allegations that it is seeking to develop atomic weapons.
On Friday, a UN nuclear monitoring mission to Iran was postponed for a week to give Tehran more time to prepare for the visit.
The delay was announced a day after it was revealed that IAEA inspectors had in August discovered more traces of highly enriched uranium in Iran, a development that could strengthen US claims that Tehran secretly seeks to make the bomb.
Iranian President Mohammad Khatami has described as "unjust" what he said was a UN ultimatum to convince inspectors that its atomic program is peaceful or face sanctions.