The United States today demanded swift action to drag Iran to the UN Security Council over its atomic ambitions, while Russia and China urged caution.
Iranian President Mahmoud Ahmadinejad began a visit to Syria in a signal to the world that the two regional allies, each facing threats of referral to the council, will not be cowed.
"On Iran, we have been very clear that the time has come for a referral to the Security Council," US Secretary of State Condoleezza Rice told reporters in Washington.
She did not mention Russia, but she was speaking a day after the European Union said it was mulling a Russian proposal that would stop short of formally referring Iran to the council.
A formal referral would mean Iran could face sanctions over the West's suspicions it is pursuing a nuclear bomb. Tehran says its only goal is to produce atomic energy for civilian use.
Moscow wants Iran to be simply "reported" to the council, which could then discuss its case but there would be a lack of legal weight and there would no potential for "consequences", EU foreign policy chief Javier Solana explained on Wednesday.
The International Atomic Energy Agency's board is due to debate Iran at an emergency meeting on February 2, but no consensus has emerged on what the UN nuclear watchdog should do.
Russian Foreign Minister Sergei Lavrov took a cautious line, saying his country's position at the meeting would be guided by the IAEA's own assessment of Iran's behaviour.
"The main principle is not to cause harm, not to cause harm to the international community, not cause harm to the system of non-proliferation," he said after talks on Iran with his French counterpart Philippe Douste-Blazy in Moscow.
Iran's Ahmadinejad has scorned a resolution drafted by EU negotiators Britain, France and Germany, asking the IAEA to send the Iranian nuclear dossier to the Security Council.
The Islamic republic is waging a high-stakes diplomatic battle with the West to head off any UN censure or sanctions.
China reiterated its preference for a diplomatic solution.
"We hope all parties will exercise restraint and patience and appropriately resolve the Iran nuclear issue through peaceful means," a Chinese Foreign Ministry spokesman said.