The permanent UN Security Council members have closed ranks by supporting a draft resolution to take Iran to the Council over a nuclear program, which the United States says hides secret nuclear weapons development.
The text on a draft resolution is a compromise between a US desire for immediate Council action against Iran, and Russia's demand for action in a month's time, until the next IAEA meeting in March.
Russia, a key trade partner of Iran, hopes diplomatic efforts can convince Tehran to respond to IAEA calls for it to suspend nuclear fuel work and cooperate fully with agency inspectors.
Russian ambassador Gregory Berdennikov indicated he would vote for the draft text and China is expected to follow the Russian lead, a Western diplomat said.
Iran defiant
Iran however has threatened to move ahead on uranium enrichment, the process used to make nuclear reactor fuel or atomic bombs, and to reduce cooperation with the IAEA if the agency goes ahead with UN referral when its meeting resumes on Friday.
Top Iranian nuclear negotiator Ali Larijani said in a letter to IAEA chief Mohamed ElBaradei: "In that case the agency's monitoring would extensively be limited and all the peaceful nuclear activities being under voluntary suspension would be resumed without any restriction."
The IAEA has called on Iran to suspend all nuclear fuel activities but Iran in January started uranium enrichment work, after having in August resumed uranium conversion that makes the feedstock gas for enrichment.
Iran's hardline President Mahmoud Ahmadinejad vowed on Thursday his country will "under no condition" abandon its disputed nuclear drive.
"The main thing in nuclear energy is enrichment," Ahmadinejad said.
Mr ElBaradei told reporters that the showdown over Iran was "reaching a critical phase but it is not a crisis situation."
Iran's nuclear program "is not about an imminent threat. I should make that very clear."
In Washington, US National Intelligence Director John Negroponte said Iran probably does not yet have a nuclear weapon and does not have the necessary material for one.
IAEA vote pending
The IAEA's board of governors is expected to vote when the meeting resumes, giving time for Europe and the United States to lobby for wide support.
US critics Cuba, Syria and Venezuela said they would vote against referral but the resolution written by Britain, Germany and France is expected to meet the US goal of rallying some 30 of the board's 35 member states.
US ambassador Gregory Schulte insisted Europe and Washington still wanted a diplomatic resolution.
Referral to the world body "will increase the diplomatic tools available to the Council," he said, adding that the United States "continues to support all efforts to seek a peaceful diplomatic solution."
The United States has sought backing for two years for taking Iran to the Council, which unlike the IAEA has enforcement powers.
The IAEA has been investigating Iran for three years, and in September found it in non-compliance with the Non-Proliferation Treaty (NPT) for hiding sensitive nuclear activities for 18 years.
Such a finding requires a report to the Security Council, but the IAEA held off on this to give Iran time to cooperate with the agency's investigation. Instead, Iran moved on January 10 to start uranium enrichment work.