Amid a din of uncompromising rhetoric from and about Iran, the UN's permanent five powers and Germany this week worked to hammer out a package of incentives and threats they hope will ensure the Islamic Republic's nuclear program is limited to peaceful purposes.
On the table: giving Iran nuclear reactors and providing fuel for energy production, as well as economic and security incentives. In exchange, Iran would have to give up uranium enrichment - a step that can lead to weapons production - or face UN sanctions or even an arms embargo.
Cutting through layers of mistrust to determine any US role - as well as Iran's ultimate goals - will not be easy, given a relationship calcified by more than 25 years of hostile rhetoric and official silence. But increasingly, analysts say that any deal ultimately depends on direct talks between the US and Iran - and possibly a US "security guarantee" that it will not attack Iran.
"If you are going to solve the problem permanently, US participation is a must," says Nasser Hadian-Jazy, a political scientist at Tehran University who was recently at Columbia University in New York. "It's like the ... elephant in the room. Everybody knows [the US] is there, but not talking about it is not going to solve the problem."
Britain, France, and Germany are spearheading the diplomatic effort on the UN Security Council. But Russia and China are loath to back sanctions that they believe could lead to an arms embargo or military action. Senior diplomats from those nations and the US reported "progress" during talks in London on Wednesday, but no agreement.
Foreign ministers of all six countries are expected to meet shortly, and Russia's National Security Council chief Igor Ivanov has been invited to meet with Iran's top nuclear negotiator Ali Larijani in coming days in Tehran.
Analysts say that "red lines" on both sides have been shifting, but that no deal is likely to stand unless the US and Iran engage in direct talks. An American "security guarantee" for Iran may be required, experts say, but so far US officials dismiss any deal that would ensure the survival of Iran's current government.
"When the US avoids giving a security guarantee [to Iran], it means they surely want to collapse and destroy the regime," says Saeed Laylaz, a political and security analyst in Tehran. "It is very good for the hard-liners in Iran. They like a critical situation in which they can say to the people: 'The United States of America is why we have trouble in the world.'"
Mr. Laylaz says that Iran would be willing to "stop" uranium enrichment completely with the right deal: a security guarantee, then getting the US directly involved in nuclear negotiations. US sanctions should be removed, he adds, and Iran integrated more fully into the global economy.
White House Press Secretary Tony Snow did not rule out the possibility of talks on Wednesday, but said that Iran would have to halt enrichment first. "When that happens, all right, then there may be some opportunities," said Mr. Snow.
The result is a dilemma for Iran. "If you know the US wants to destroy you, and the four borders of your country are occupied by the US military, you know that you should accelerate your uranium enrichment, not suspend it," says Laylaz. "But at the same time, [Iranian officials] are asking the US: 'Please come to the table and start negotiating.' Because they realize there is no country in the world ... that can stop the US if it wants to militarily attack Iran."
Mohamed ElBaradei, the head of the UN's International Atomic Energy Agency (IAEA), indicated during talks on Wednesday with US Secretary of State Condoleezza Rice that Iran might delay enrichment plans for five or six years and accept the intrusive inspections of the "additional protocol" of the nuclear Non-Proliferation Treaty (NPT).
"The default position in Iranian foreign policy is hard-line, and you have to work hard to bring it the other way," says Shahram Chubin, director of studies at the Geneva Centre for Security Policy.
"The hard-line conservatives in Iran believe that dealing with the Americans and the West is a contaminating thing, that you are going to give up all your values, and end up being ... a nothing," says Mr. Chubin. "And the whole essence of the revolution is as an example, a model in the Islamic world. They have a vanguard reputation, and they're not going to give it up - there is a lot there."
Still, Iran has been signaling that it wants to talk. President Mahmoud Ahmadinejad sent a letter to Mr. Bush on May 8, the first such high-level public contact since Iran's 1979 Islamic revolution. Though it was full of tough and critical talk, experts suggest that a Bush response - ruled out for now - could be first steps toward dialogue.
One day later, another letter from Iran's former top nuclear negotiator, Hassan Rohani, who remains the influential representative of Iran's top religious leader on the Supreme National Security Council, was published in Time magazine, taking a "good cop" tone to Mr. Ahmadinejad's "bad cop."
"Iran is intent on producing nuclear fuel domestically for reasons both historic and long-term economic," he wrote, laying out an eight-point plan for a negotiated solution.
Past failures to declare aspects of nuclear programs "are not uncommon among NPT members," and "an Iranian secret weapon program is only hype," Mr. Rohani wrote. "A solution imposed on Iran by the Security Council is unlikely to provide assurances the US seeks about the Iranian nuclear program."
Iran has enriched small quantities of uranium to levels needed for nuclear fuel in recent weeks, using a cascade of 164 centrifuges. Iran wants to start two more such pilot projects in coming months - before beginning production with tens of thousands of centrifuges to fuel a Russian-made reactor at Bushehr. That reactor should be completed later this year. .
Ahmadinejad on Wednesday claimed that Iran had mastered "the entire nuclear fuel cycle from start to finish," and that it would never give it up.
"The minimum [acceptable to Iran] would be at least to have this 164-centrifuge cascade running - this is a red line," says Mr. Hadian-Jazy. The US holds that all enrichment must stop; some Europeans and IAEA diplomats say that is unrealistic.
"Is it worth - and I'm talking about both parties--to go to war for one cascade?" asks Hadian-Jazy. "[Iran] is ready to give a more intrusive inspection regime, real-time monitoring, ratifying the Additional Protocol, accepting some transparency measures..."
The picture in Iran is further clouded by local politics. "When you ask, 'What do the Iranians want?' the answer is: 'Which Iranians?' " says Chubin at the Geneva Centre. "It's certainly true that Rohani and [former president and head of the powerful Expediency Council Ali Akbar] Rafsanjani believe Iran should use the leverage of their ... program to cut an overall deal with the West.
"The other view, of Ahmadinejad and Larijani, is that: 'We've got the power; we don't need anyone's help with our own security,' " says Chubin. "They want nuclear weapons to be the leading power in the region, in order to be in opposition to the West, and they have no interest in a global grand bargain."
And there is another player, whose vote in Iran counts above all others: Supreme Leader Ayatollah Ali Khamenei. "They don't want a military attack," says analyst Laylaz. "It's not the hard-liners' [red line], but the Leader's red line."
"I'm not sure about US policy toward Iran," adds Leylaz. "If they test a potential negotiated way, and ask strongly to suspend any uranium enrichment, we can avoid a catastrophe. Otherwise, I'm not sure about the future."