ElBaradei noted that the IAEA had seen an increased level of co-operation from Iran in answering questions about the past, but its knowledge of Tehran's current programme has "diminished" since 2006.
The main bone of contention in the nuclear stand-off is Iran's adamant refusal to suspend its enrichment activities, a potential pathway to developing the atom bomb.
"America says Iran getting a nuclear weapon could cause WW3 but I think it's more likely that America would cause WW3 by invading Iran"
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In fact, Tehran has actually stepped up such activities in defiance of UN demands to stop or face fresh sanctions.
Later on Thursday, the United States' three key European allies said that Iran had not done enough to win trust in its atomic work and the UN should now consider tougher sanctions.
"A wait-and-see approach is not an option," Britain, France and Germany told the IAEA's governors.
Commenting on ElBaradei's remark that IAEA's knowledge of Iranian nuclear activitiy is shrinking and that Iran is expanding uranium enrichment, the "EU-3" said both matters were "unacceptable".
"We are interested at least as much in the present and future [of Iran's programme] as the past," their statement said.
On Tehran's part, Saeed Jalili, the country's nuclear negotiator, said on Thursday that he would meet Javier Solana, the EU foreign policy chief, on November 30.
Solana confirmed that the talks were "very likely".
Solana also said international nuclear fuel production sites are an idea that should be examined to help defuse the stand-off.
"The idea of international enrichment centres under multilateral supervision has been discussed for some time. Let us therefore try to deepen it," he said.