Even the Russian government is piling on pressure, with a news leak claiming Secretary of State Hillary Rodham Clinton sent a stern warning to Tehran via Moscow. Her supposed message: These talks are a "last chance" to peaceably resolve the nuclear standoff. State Department spokeswoman Victoria Nuland denied that Clinton used the word last, but confirmed she meant the talks "can't be used for stalling" - and must be structured for results.
True, the history of such talks over the last decade isn't encouraging. Iran has refused to allay the suspicions of U.N. nuclear inspectors that its program is building the capacity to produce weapons. And Iran has enriched far more nuclear materiel than is needed for peaceful use.
Iran did come tantalizingly close in the fall of 2009 to a "magic compromise" on its nuclear program. The terms of the deal were described to me by Michael Adler, perhaps the best-informed U.S. journalist on the tangled tale of nuclear diplomacy.
Iran would have shipped most of its low-enriched uranium out of the country to be turned into fuel rods for its research reactor. While Tehran could have continued to enrich uranium, it would have taken a year to restore the amount required, in theory, for a weapon. This would have provided time to negotiate further checks on the program.
The chief Iranian negotiator, Saeed Jalili, signed off on the deal, which presumably had a green light from Iran's supreme leader, Ayatollah Ali Khamenei. But internal Iranian politics killed the deal, says Adler, now writing a book on nuclear diplomacy at Washington's Woodrow Wilson Center.
Since then, diplomacy has gone nowhere, even as Iran began enriching some uranium to higher levels. But circumstances may be more propitious now. Here's why:
First, Iran is feeling the pressure from severe U.N. and international sanctions that target its banks and oil sales, and more sanctions are on tap. Iran has developed ways to partially circumvent sanctions, but its leaders concede they hurt.
Second, these economic strains occur at a time when Iranian efforts to dominate the region have been sharply undercut by the Arab Spring and by the turmoil inside Tehran's only Arab ally, Syria.
Third, Iran's leaders must consider the cost of a military strike to their country. They insist a strike wouldn't end their nuclear program (and it probably would strengthen the regime). But they know they can't fully calculate the repercussions of an attack.
So, Ayatollah Khamenei must be rethinking his options.
This may account for an extraordinary interview given last week to CNN by Mohammad Javad Larijani, a key adviser to the supreme leader, in which he hinted at Iranian concessions. He repeated that Khamenei had issued a fatwa against nuclear weapons. (If this is true, the Iranians should publish the fatwa.) He also insisted that President Mahmoud Ahmedinejad's rhetoric didn't mean that Israel should be "wiped from the map" militarily "nor is it a policy of Iran."
Of course, words mean little until backed up by actions. Iran is a master at manipulating talks. And it will be much harder to formulate a "magic compromise" now than in 2009, since Tehran has produced far more uranium since then. Any deal would have to take place in phases; Iran would have to come clean about suspected weapons programs before any sanctions were lifted, even partially.
Many experts believe anti-Americanism is so integral to Iran's ideology that Khamenei will be incapable of compromise, especially if oil prices remain high. Meantime, U.S. war hawks will be pressing Obama to give talks short shrift, lest Iran take advantage.
One thing is certain: The window for diplomacy won't stay open for long, nor will the West let talks drag on indefinitely. As Adler puts it, "The administration is committed to reaching a diplomatic solution, but [diplomacy] does not have an eternal shelf life."
If negotiations are to stand a chance, Iran must signal it is serious, and soon.
E-mail Trudy Rubin