Iran's abrupt resumption of its nuclear program this week, throwing Tehran's clerical regime into open conflict with the rest of the world, appears to have doomed current diplomatic efforts to curb the country's nuclear ambitions.
Ending a two-year freeze on research into uranium enrichment - an essential step in the production of both nuclear reactors and bombs - Iranian officials reopened the Natanz nuclear research facility on Tuesday. European leaders who had negotiated the research suspension said the move marked the end of their readiness for talks.
Foreign ministers from Britain, France, and Germany, whose two years of diplomatic efforts failed to persuade Iran to drop uranium enrichment permanently, are expected to launch a bid Thursday to refer Iran to the UN Security Council, which could enforce economic and political sanctions. There are signs, for the first time, that Russia and China may not stand in their way.
"We were in crisis management mode, offering dialogue," says a European diplomat close to the negotiations. "Now we have gone through every single red line. We have to move to another stage."
"The European Union door is shut and the Iranians have thrown away the key," added Ali Ansari, an expert on Iranian politics at St. Andrew's University in Scotland. "This was a symbolic slap in the face for the Europeans."
Iran insists its nuclear program is only for peaceful, electricity-generating purposes, and that it therefore has the right under the Nuclear Non-Proliferation Treaty (NPT) to develop the full nuclear fuel cycle.
The US, increasingly supported by EU nations, claims Tehran is seeking to build a nuclear bomb. It is also worried by Iran's program to develop a long-range missile that could deliver it to Vienna - or Israel.
A three-year probe by the International Atomic Energy Agency (IAEA) has found no hard evidence that Iran is seeking a nuclear weapon but has raised many unanswered questions. Chief among them is why the Iranian authorities hid large parts of their nuclear program for years, before they were revealed by an exile opposition group in 2002.
"I am running out of patience, the international community is running out of patience" with Iran's evasiveness over nuclear issues, IAEA chief Mohammed ElBaradei told Britain's Sky News television earlier this week.
If enriched to a low level, uranium can be used in power stations. But enriched to a higher degree, it can be used in nuclear warheads. To reassure the world of its peaceful intentions, Iran promised its European negotiating partners in October 2003 to suspend all activities related to the enrichment of uranium in return for political and economic incentives. Iran broke that pledge Tuesday.
While Washington and European governments appear ready to push for United Nations sanctions, which can be imposed only by the UN Security Council, Russia and China - both veto-wielding members of the Council - appear more cautious.
Traditionally Moscow and Beijing have been sympathetic to Tehran, but European diplomats had some success in winning their understanding.
Both China and Russia wrote letters to the Iranian government last weekend urging it to maintain its enrichment moratorium. Tuesday's move snubbed both.
Russian Defense Minister Sergei Ivanov said Wednesday he was "disappointed and worried" by Tehran's decision, which he added was "not following the best case scenario." In Beijing, the chairman of China's National People's Congress, Wu Bangguo, told visiting US lawmakers Wednesday that his government "agreed to working with the United States and especially the EU3 on Iran," according to Mark Kirk, a Republican Congressman.
Recent inflammatory comments by Iranian President Mahmoud Ahmadinejad attacking Israel and calling the Holocaust into doubt have not helped Iran's cause abroad. "Ahmadinejad has given them (the Americans) an open goal," says Dr. Ansari. "Even the Russians and the Chinese are getting fed up."
The first test of the diplomatic waters will come at the "extraordinary" meeting of the IAEA board which the European foreign ministers and EU foreign policy czar Javier Solana are expected to call for on Thursday, after consulting with US Secretary of State Condoleezza Rice.
At the IAEA, Russia may seek to delay a referral of Iran's nuclear program to the UN Security Council because Moscow is still offering one possible way out of the crisis - a proposal that Iran's uranium be enriched in Russia, to ensure that none of it is diverted to illegal military purposes.
Iran hasn't rejected the idea, and is due to send a delegation to Moscow on Feb. 16 to discuss it further. But some observers think Iranians won't take the offer seriously, against a background of prickly relations.
"The history of Iranian-Rusisan is pretty appalling. It's not a track record you'd want to rely on," says Dr. Ansari.
If Iran is referred to the Security Council for violating the NPT by hiding much of its nuclear program for two decades, members will face a number of sanctions options, ranging from a suspension of economic ties to breaking diplomatic relations with Tehran.
None of them is pain-free for the international community, however, say observers.
"Interrupting diplomatic relations would send a powerful signal but its consequences would not be obviously favorable to us, since we would lose direct knowledge of what was going on in Iran," points out François Heisbourg, head of the Strategic Research Foundation, a think tank in Paris.
Refusing to buy Iranian oil - another option - would raise international oil prices to levels that would threaten the world economy, he adds. The Russians, too, are cautious about sanctions, says Yevgeny Bazhanov of Moscow's Diplomatic Academy.
"We're not against sanctions, but think they should be ... targeted to solve the problem. We wouldn't support blanket punishment, or ultimatums, but only sanctions that really work," says Mr. Bazhanov.
The EU is anxious to steer the crisis towards the United Nations if only to head off the prospect of an Israeli strike on Iran's nuclear facilities.
Though some US voices have been raised in favor of a military strike against Iranian nuclear installations, such an attack would undoubtedly prompt Iran to use all its considerable influence among Shiite Muslims in Iraq to undermine US goals there.
"The diplomatic game is the only game in town" when it comes to dealing with Iran's nuclear program, argues Mr. Heisbourg. "It is not working, but I know of no other."
• Fred Weir contributed from Moscow.