Even non-aligned nations sympathetic to Iran seemed ready to sign on to a draft resolution Europe's big three -- Britain, France and Germany -- are to present when the International Atomic Energy Agency's (IAEA) 35-nation board of governors opens what could be a week-long meeting in Vienna.
The resolution raps Iran for hiding sensitive nuclear activities but also presses for continued cooperation with Tehran.
Iran is preparing itself for a souring in ties with the IAEA as Tehran refuses to renounce its right to enrich uranium for nuclear fuel, Seyed Hossein Mussavian, a member of Iran's Supreme National Security Council, told the Iranian student news agency ISNA Sunday.
"We are entering into a second phase which is the challenge posed by enrichment," Mussavian said, adding that this was difficult since "the Americans and the Europeans are on the same side".
"The Europeans are saying that in order to be sure that nuclear fuel is not used to produce nuclear weapons, Iran must renounce enrichment.
"But Iran considers enrichment to be an absolute right in the Non-Proliferation Treaty (NPT) and Iran is not ready to renounce this," Mussavian said.
Highly enriched uranium (HEU) can be used as nuclear fuel but also to make a nuclear bomb.
Tehran has agreed to suspend enrichment as a confidence-building measure but has insisted the suspension is only temporary and continued to work on other key parts of the sensitive nuclear fuel cycle.
Mussavian said the Euro-3 draft resolution signifies "that the Europeans, the IAEA and the Americans have a tacit agreement to keep the dossier at the top of the agenda so that the suspension of enrichment is longer."
He demanded it be amended, and Iranian diplomats were lobbying for this in Vienna.
"Everyone realizes what's at stake," a diplomat close to talks on the resolution told AFP about the need to determine whether Iran is hiding a nuclear weapons program, as the United States claims, or developing nuclear power for peaceful purposes, as Tehran says.
The diplomat said "no one questions the work of the agency" in finding omissions and discrepancies in Iran's reporting on its atomic activities.
And no one, except Iran, thinks the Iranian issue can be decided this June, the diplomat said, as the investigation is far from being completed.
The board meeting will also review Libya, with the IAEA vowing to persist in investigating Tripoli's now abandoned nuclear weapons program, as much to discover new facts about Libya as about the international smuggling network that supplied it, as well as Iran.
A tough Washington-inspired IAEA board resolution in March had condemned Iran for omitting to report its work into sophisticated P-2 centrifuges which can enrich uranium to bomb-grade levels.
But it drew protests from Iran that included delaying crucial agency investigations, a delay that makes it difficult for the IAEA to draw conclusions this June.
The United States looks ready to sign on this time to the Euro-3 draft resolution as it feels the tough language is "moving towards where the United States wants to be."
The United States wants to cut off cooperation with Iran and take it to the UN Security Council for possible sanctions but Washington does not have support at the IAEA for its hardline stance.
Diplomats said however that even the EU-3 were getting impatient with Iran, as the IAEA has been investigating the Iranian program since February 2003 with Iran consistently failing to deliver on promises for full disclosure.