Updated

Iran's chief nuclear negotiator told the head of the International Atomic Energy Agency Thursday that his country would severely curtail the agency's inspections of Tehran's atomic program and resume uranium enrichment if referred to the to the U.N. Security Council.

The warning to the IAEA chief Mohamed ElBaradei from Ali Larijani, Iran's top nuclear negotiator, was contained in a letter made available to the Associated Press.

Meanwhile, U.S. and European diplomats campaigned behind the scenes in a last-minute effort to gain the broadest possible consensus for reporting Iran to the Security Council.

The negotiations came as the IAEA's 35-nation board of governors began a two-day meeting on a European draft resolution calling for Tehran to be referred to the Security Council, which can impose sanctions.

Diplomats at the meeting said adoption of the resolution within the next few days was certain, but Washington and the European Union, the key backers of referral wanted to build as much support as possible.

State Department spokesman Sean McCormack said Thursday talks would likely take "a day or so" to finish.

"We believe we have a solid majority for the resolution," he said in Washington, adding he expects it would be "low to single digits that would vote with Iran."

The chief of the U.N. nuclear watchdog agency, Mohamed ElBaradei, said the meeting opened a "window of opportunity" to defuse the crisis, stressing that even if the issue is referred, the Security Council would not take up the issue before next month.

"We are reaching a critical phase but it is not a crisis," he told reporters.

The IAEA board was expected to approve the motion easily because Russia and China — which have veto power on the Security Council along with the U.S., Britain and France — now support reporting Iran following months of opposition. But protracted back-room negotiations were being held to achieve broader consensus.

Grigory Berdennikov, Russia's chief IAEA delegate, reinforced Moscow's position outside the meeting, telling reporters that referral to the Security Council would send Iran "a serious signal.

Chief U.S. delegate Gregory L. Schulte agreed.

"It is time to send a clear and unequivocal message to the Iranian regime about the concerns of the international community by reporting this issue to the Security Council," he said.

Washington has waited years for international suspicions over Iran's nuclear ambitions to translate into support among board nations.

Only a simple majority is needed to approve the text, but America and its key backers have held off pushing for earlier referral in hopes of building support for the measure.

While a broad majority of member nations support referral, a handful of countries that have major policy disputes with the Americans remain opposed — among them Cuba, Venezuela, Syria and Belarus.

"My delegation manifests its total disagreement with the proposal ... to bring it to the Security Council," chief Venezuelan delegate Gustavo Marques Marin said, reflecting the view of dissenting nations.

A vote could be delayed until Friday, possibly even Saturday, as diplomats accredited to the meeting said the draft could still undergo small-scale modifications to gain more support.

Diplomats said India, which had been opposed, was leaning toward supporting the draft now that China and Russia had signed onto it. Countries opposed have the choice of directly voting against the text or abstaining.

Speaking for Germany, Britain and France — the three nations representing the European Union — German chief delegate Herbert Honsowitz told the meeting: "The time now has come for the Security Council to get involved."

Iran's decision Jan. 10 to restart small-scale uranium enrichment — and Iranian President Mahmoud Ahmadinejad's recent calls for Israel to be wiped off the map — apparently rattled Beijing and Moscow enough to support the U.S. position. Iran became more insistent on its right to pursue a nuclear program and less cooperative in talks with European negotiators after the election of the hard-line Ahmadinejad last June.

The call for referral was contained in a confidential draft resolution obtained by AP. It "requests the director general to report to the Security Council" on steps Iran needs to take to dispel international suspicion it could be seeking to manufacture nuclear arms.

The draft expresses "serious concerns about Iran's nuclear program" and notes "the absence of confidence that Iran's nuclear program is exclusively for peaceful purposes."

If the board approves referral as expected, it will launch a protracted process that could end in Security Council sanctions for Tehran.

"I am making very clear that the Security Council is not asked at this stage to take any action," ElBaradei said.

Moscow and Beijing support referral only on condition that the council take no action until at least March, when the board next meets to review the status of an IAEA probe into Iran's nuclear program and recommends further action.

Berdennikov, the Russian delegate, emphasized his country's position on the delay, telling reporters Moscow "insists" no Security Council action be taken before March.