The United Nation's nuclear watchdog, the International Atomic Energy Agency (IAEA), is to consider the move, which could expose Iran to punishing sanctions, when the agency's 35-nation board of governors meets Thursday in Vienna.
The United States accuses Tehran of secretly trying to develop nuclear weapons and wants the issue to go to the Security Council but most IAEA board members, led by Britain, France and Germany, oppose this, diplomats said.
IAEA chief Mohamed ElBaradei said in a report last week that while Iran has violated international safeguards for 18 years by hiding nuclear activities that included making plutonium and enriched uranium, there was so far no evidence it is trying to make the bomb.
Britain, France and Germany have repeatedly urged opening up a dialogue with oil and gas-rich Iran while the United States does not even have diplomatic relations with the Islamic Republic.
A visit by the three European countries' foreign ministers to Tehran on October 21 won 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.
Iran's IAEA ambassador Ali Akbar Salehi told AFP Saturday that Tehran had in October reached "an understanding" with Britain, France and Germany that it would be rewarded for its cooperation by not being taken to the Security Council.
"There has been an understanding and I'm sure that this part of the understanding is well received by the majority of the (IAEA) board," he said.
He said it was a "matter of principle" for Iran since Iran has "admitted our failures" and these had been "rectified and corrected."
Salehi said Iran "has gone to the extreme to win the trust of the international community. What else can Iran do?"
He warned that an IAEA finding that Iran is in non-compliance with the nuclear Non-Proliferation Treaty (NPT), a ruling that would automatically send the matter to the Security Council, would "escalate the issue into an international crisis."
Diplomats said Iran could back off from its pledge to sign an additional protocol on unannounced inspections or could resume uranium enrichment.
Britain, France and Germay are drafting a resolution for Thursday's meeting which would criticize Iran for its past failures to comply with NPT safeguards but avoid declaring it in non-compliance, diplomats said.
A diplomat said the formula might be "to make a severe judgement of Iranian lack of cooperation until October 21" but to acknowledge Tehran's cooperation since then.
The resolution would say that "Iranian cooperation must intensify within the framework of the additional protocol" to the NPT, that authorizes a rigorous inspection regime designed to prevent a country from hiding a weapons program.
The EU, Russia, non-aligned and even some Latin American states are believed to back this approach, with the United States, Canada and Australia insisting that Iran, due to its long history of of covert activities, must be declared in non-compliance if the NPT treaty is to have any meaning.
A Western diplomat said that the Russians, who have a multi-million dollar contract to build a nuclear power reactor in Iran, are particularly "afraid of strong language.
He said a non-compliance resolution could be worded in such a way that sanctions against Iran are not threatened and Tehran is given credit for cooperation.
But a diplomat for a non-aligned country said ElBaradei had not said in his report that Iran was in non-compliance and "a compromise would be to use the director general's language."
However a Western diplomat said: "The Iranians have done new and welcome things, and that has to be recognized. But that doesn't erase the past.
"It would be a bad precedent if we pretended that the past never happened."