WASHINGTON -- The presidents of America and Iran may meet briefly next week for the first time, marking a symbolic but significant step toward easing their countries' tense relationship. An exchange of letters between the leaders already has raised expectations for a thaw in relations, and any progress in dismantling Syria's chemical weapons stockpile could signal whether their elusive diplomacy will last longer than a handshake.
At the heart of the U.S.-Iran impasse is a years-long dispute over Tehran's nuclear program.
In small steps and encouraging statements, Iran's leaders appear to be opening wider a door to detente. Cautiously optimistic yet still skeptical, Washington is weighing whether Iranian President Hassan Rouhani's recent overtures actually represent new policies or just new packaging.
"Negotiations with the Iranians is always difficult," President Barack Obama said in a recent interview with ABC News. "I think this new president is not going to suddenly make it easy. But, you know, my view is that if you have both a credible threat of force, combined with a rigorous diplomatic effort, that, in fact, you can strike a deal."
Both Obama and Rouhani will be in New York next week for the annual meeting of the U.N. General Assembly. The White House hasn't ruled out the possibility of a direct exchange, though spokesman Jay Carney said no meeting is scheduled.
Obama has long said he would be open to discussions with his Iranian counterparts if Tehran shows it is serious about curbing its nuclear program.
"There have been a lot of interesting things said out of Tehran and the new government -- and encouraging things," Carney said Thursday. "But actions speak louder than words."
Iran insists its nuclear program is peaceful and that it is enriching uranium to levels needed for medical isotopes and reactor fuel. But Western powers, including the U.S., fear Iran is trying to build a nuclear bomb.
Whether any headway is made on the nuclear issue could hinge on how the U.S. and Iran handle negotiations to dismantle Syria's vast chemical weapons stockpile. Iran is the chief benefactor to Syria, where an Aug. 21 chemical weapons attack on Damascus suburbs killed as many as 1,400 people, according to U.S. and Western intelligence agencies, who blame the government of Syrian President Bashar Assad.
Yet Iran has been vociferous in its condemnation of chemical weapons attacks in Syria. In an interview with NBC News that aired this week, Rouhani called for "the elimination of all weapons of mass destruction in the entire region." He also said that Iran, "under no circumstances, would we seek any weapons of mass destruction, including nuclear weapons, nor will we ever."
Robert Einhorn, who left the State Department in May after serving as special adviser for arms control and a negotiator on the talks with Iran, said the nuclear discussions could dissolve if the Syria plan fails.
"I think the American public, the American Congress would say, `Oh, you've got to be kidding. ... Look what happened last time. The Syrians weren't serious; do you think the Iranians are serious about diplomacy? They're just going to play this out, they're going to play for time and advance their nuclear program, just the way the Syrians did on the chemical weapons,'" Einhorn, now at the Brookings Institution, said last week at the Atlantic Council think tank.
"On the other hand, if you had a good deal, if the current efforts resulted in the end of Syria's chemical weapons program -- verifiably, credibly and quickly, with the absence of military action -- I think this could have very positive implications on prospects of diplomacy and willingness to take a risk on diplomacy in the case of Iran," Einhorn said.
Since Rouhani's election in June as the Islamic Republic's president, he and Obama have exchanged letters in what U.S. officials describe as an encouraging easing of Iran's defiance of the U.S. In contrast to his recalcitrant predecessor, Mahmoud Ahmadinejad, Rouhani is widely seen as a moderate politician who may have more autonomy to govern under Iran's supreme leader, Ayatollah Ali Khamenei.
It's unclear how many letters Obama and Rouhani have exchanged. The U.S. president sent at least one letter after Rouhani's inauguration in early August and Iranian officials say the new president did respond.
White House officials said Obama's letter to Rouhani touched on the long-stalled negotiations over Tehran's nuclear program, one of the main roadblocks to diplomacy between the two countries. Officials said Obama indicated that Washington was ready to resolve the nuclear issue in a way that would allow Iran to demonstrate that its program was exclusively for peaceful purposes.
"The letter also conveyed the need to act with a sense of urgency to address this issue because, as we have long said, the window of opportunity for resolving this diplomatically is open, but it will not remain open indefinitely," Carney said.
Rouhani, in his first interview with a Western media outlet, told NBC News that he thanked Obama for his outreach and "expressed Iran's viewpoint on the issues raised in his letter and some other issues."
In 2009, shortly after taking office, Obama also wrote to Khamenei expressing a desire for a different type of relationship between their countries. People familiar with the outreach say Khamenei responded with a letter of his own but gave little ground and, ultimately, the communications fizzled.
Einhorn also predicted that negotiators from the U.S. and Iran will sit down for direct one-on-one talks about the nuclear issue in the near future -- a direct negotiation that he said has not happened since 2009.
Any direct exchange between Obama and Rouhani at the United Nations would be largely symbolic, with substantive negotiations on Iran's nuclear program almost certainly reserved for talks with officials from both governments.
Trita Parsi, the president of the National Iranian American Council, said Rouhani has a narrow window of opportunity to show the U.S. and the international community that he's more serious about negotiations than his predecessors.
"He doesn't have much time to show that his approach is more effective than the regime previously," Parsi said. "It's important for him to present something at the U.N. that is very memorable, that really adds to what he has already been doing over the last couple of weeks."