The UN nuclear watchdog is expected to issue a report to the Security Council later today on whether Iran has suspended sensitive nuclear work.
There are concerns Mr ElBaradei's comments could weaken UN resolve
The Council imposed a second round of sanctions on Iran in March, for failing to suspend uranium enrichment.
It then asked the IAEA to report within 60 days on whether Iran had complied.
The Security Council fears Iran is secretly trying to develop nuclear weapons. Tehran continues to insist on its right to enrich uranium.
The deadline comes amid reports that the US is to complain to the International Atomic Energy Agency's chief, Mohamed ElBaradei, about his proposal that Iran keep parts of its enrichment programme.
Mr ElBaradei said Iran possessed "the knowledge about how to enrich" and the focus should now be on preventing industrial-scale production.
But there are concerns his comments will weaken UN resolve to punish Iran over its nuclear activity.
Envoys from the US, France, Germany and Britain are expected to visit Mr ElBaradei this week to deliver a formal complaint that the agency chief's comments "were not helpful", a US official told Reuters on condition of anonymity.
In an interview with the New York Times last week, Mr ElBaradei said: "The focus now should be to stop [Iran] from going to industrial-scale production, to allow us to do a full-court-press inspection and to be sure they remain inside the treaty."
He has previously said that Iran would not be able to produce the highly enriched uranium needed for a nuclear bomb as long as it remained under the supervision of IAEA inspectors.