"We are still discussing the additional protocol" to the nuclear Non-Proliferation Treaty (NPT), Iranian foreign ministry spokesman Hamid-Reza Asefi said.
Tehran is under strong international pressure to prove it is not secretly developing atomic weapons by signing the extra clause, which would allow UN inspectors to descend on suspect sites without warning.
"Any decision will depend on the explanations given by the agency, on the ambiguities that exist (over the additional protocol), our responsibilities and those of the international community with regard to Iran," he added.
The Iranian nuclear case will be reviewed by the IAEA's board of governors on September 8, with the threat that the case might be forwarded to the UN Security Council.
Asefi told reporters "to wait and see what will happen during the (September 8) meeting."
"For the moment, we are discussing the matter with the agency," he added.
IAEA inspectors arrived in Iran last week to carry out final checks before the crucial meeting.
The Iranian press has quoted diplomatic sources as saying they found traces of enriched uranium.
Questioned about this, Asefi said: "It was not up to the diplomats to speak about such a technical and expert subject without knowing the details. It is up to the agency to judge and to give its point of view. We will wait until September."
Tehran also invited IAEA experts to Iran earlier this month to explain the implications of the additional protocol.
"The Islamic republic was serious and transparent in its cooperation with the IAEA. The recent two missions of the agency is proof of our sincerity and the veracity of our declarations," Asefi said.
"We hope that this cooperation will cause the agency and the board of governors to have give a precise and right judgment" on Iran's nuclear program, he said.
On Wednesday Iran's atomic energy chief, Gholam-Reza Aghazadeh, said the two sides should reach "positive" results by September.
He said discussions with IAEA experts had eased "some of Iran's uncertainties" with regard to the protocol, particularly over military secrets and strategy.
Some conservatives oppose the signing of the additional protocol, and have called on Tehran to renounce the treaty, fearing inspectors would use it to violate national secrets.
Oil-rich Iran said Thursday it was going ahead with the second phase of a nuclear power plant to satisfy its growing demand for power and prevent long-term energy shortages, denying US allegations that it is covertly developing nuclear weapons.