The head of the UN's nuclear watchdog says he has seen no firm evidence Iran is secretly developing nuclear weapons.
The IAEA chief says the situation may be no clearer by November
But International Atomic Energy Agency chief Mohamed El-Baradei said he could not yet give assurances Iran's nuclear programme was entirely peaceful.
"Have we seen any proof of a weapons programme? Obviously until today there is none of that," he said.
Tehran says its nuclear programme is used solely for the purpose of generating electricity.
Mr El-Baradei - at an IAEA meeting in Vienna to discuss Iran - said: "Are we in a position to say that everything now is peaceful? Obviously we are not at that stage."
Britain, France and Germany have submitted a draft resolution to the IAEA giving Iran until November to prove it is not lying about its nuclear intentions.
The European trio has already been involved in delicate negotiations to persuade Iran to abandon its nuclear ambitions.
But Mr El-Baradei cautioned against any imposed deadline.
The IAEA has been carrying out an investigation to try and find out the extent of Iran's nuclear programme and whether it is secretly trying to build a nuclear weapon.
The ongoing inquiry is highly complex, he said, explaining it depended on information provided by Iran as well as countries who supply nuclear material on the black market.
"There is no artificial deadline whereby I can say in November, I can promise that everything will be completed," he said.
The IAEA chief said he would be ready to give an evaluation on Iran's nuclear programme by then but added: "I am giving advance warning that this will not be the end of the story."
Iran says abandoning uranium enrichment is "out of the question" but it is prepared to give assurances that it will not build nuclear weapons.
The United States has led concerns that the Islamic republic is developing a nuclear industry which could be used to build weapons.
Washington wants the issue to go to the UN Security Council which has the power to impose sanctions.