EU foreign policy chief Javier Solana said Iran had been "honest" in its nuclear dealings with the international community.
Solana, speaking ahead of talks in Brussels with Iran's top national security official Hassan Rowhani, said he expected the International Atomic Energy Agency (IAEA) to stop short of calling for the Security Council to rebuke the Islamic republic.
Rowhani said after meeting foreign ministers of Britain and France, and a senior Germany official, in Brussels that "there is no justification, no reason to refer Iran's peaceful nuclear programme" to the Security Council.
The United States accuses Tehran of secretly trying to develop nuclear weapons and wants the issue to go to the Security Council.
ElBaradei (L) has given a clean
chit to Iran on issue of N-bomb
But most members, led by Britain, France and Germany, of the 35-nation IAEA board of governors meeting on Thursday oppose this. They want to reward Tehran for cooperating with the atomic agency, diplomats said.
In Moscow, Russia's Atomic Energy Minister Alexander Rumyantsev said international sanctions against Iran would be "unacceptable," as Tehran had been open about its nuclear programme.
IAEA chief Muhammad ElBaradei said in a recent report that while Iran had violated international safeguards by hiding nuclear activities that included making plutonium and enriched uranium, there was so far no evidence it was trying to make a nuclear bomb.
"The Americans may think no (IAEA board) resolution is better than a weak one for fear of weakening" the nuclear Non-Proliferation Treaty (NPT), which authorises the IAEA to enforce international nuclear safeguards, a Western diplomat said.
Another diplomat said the US was holding off on offering a counter-resolution to one being prepared by Britain, France and Germany since it does not think it has a consensus for its position.
The foreign ministers of Britain and France on a visit to Tehran on 21 October secured key concessions, including Iran's full disclosure of its past nuclear activities, a pledge to accept tougher inspections and a suspension of the enrichment of uranium.
Diplomats, as well as Iran's ambassador to the IAEA, said a deal was struck in Tehran that Iran would be rewarded for cooperation by being spared a citation for non-compliance before the Security Council.
The Iranian ambassador, Ali Akbar Salehi, has warned that an IAEA non-compliance finding would "escalate the issue into an international crisis."