"Overall I think we are moving in the right direction," ElBaradei told a French parliamentary hearing during a visit to Paris.
"But Iran also has to understand that the world is not going to wait forever for them to come clean," ElBaradei said. "There is also the credibility of the verification, and people are getting a bit impatient.
Iran reiterated Wednesday that it would stick to its commitments to cooperate with the International Atomic Energy Agency (IAEA) over its nuclear programme.
With IAEA inspectors due to report on Iran's activities by the end of May, Foreign Minister Kamal Kharazi, speaking in Berlin on Wednesday, pledged that Tehran would "fulfill our commitments on the nuclear programme."
ElBaradei said cooperation had improved since October, when Iran gave the IAEA what it said was a complete declaration of its nuclear activities but the dossier was later found to have significant omissions.
But the IAEA chief recalled Tehran's suspension of inspections in March "after a resolution by our board of governors which they did not like."
The IAEA resolution condemned Iran for failing to report crucial technologies such as designs for sophisticated centrifuges that can produce weapons-grade uranium.
ElBaradei was to meet later Thursday with French Foreign Minister Michel Barnier.