In a March meeting with nuclear scientists, Khamenei said that Iran considers the possession of nuclear weapons to be a sin and that the country would not pursue them.
Iranian media have also reported that Khamenei issued a fatwa, or religious ruling, against such weapons.
But amid escalating tensions with the West over Tehran's nuclear program, which the country's leaders insist is for peaceful purposes, the reported fatwa is being scrutinized anew.
Will the alleged ban hold up in practice and under all circumstances? Can the fatwa be reversed?
Those questions are being debated by analysts in the West, but also among regime supporters inside Iran.
Teribon.ir, a hard-line Iranian website, recently asked, “Aren’t nuclear weapons needed to preserve the Islamic establishment?”
The website was referring to comments made by the founder of the Islamic republic, Ayatollah Ruollah Khomeini, who said that preserving the Islamic establishment is an obligation that supersedes all others.
"If regional and international conditions become such that Iran will find it necessary to build nonconventional weapons for its own survival," Teribon.ru asked, "would it be permissible to build nuclear weapons?"
An Iranian cleric and researcher, Hojatoleslam Hossein Ali Salmanian, who was interviewed by the website, suggested that nuclear weapons cannot function as a tool for the preservation of the Iranian establishment.
“Nuclear weapons will also threaten us. It is likely that they will lead to the death of people in the Islamic republic and elsewhere in the world. They won’t help at all to preserve our establishment," said the cleric. He noted that a nuclear weapons capability did not prevent the collapse of the Soviet Union.
"What if [Iran] is attacked in a way that it has no choice but to use nuclear weapons?" Teribon.ru asked in a follow-up question.
Some observers have warned that an attack on Iran's nuclear facilities could lead the country to pursue nuclear weapons, prompting a reversal of Khamenei's ruling.
Salmanian responded by saying he didn't believe the United States or Israel would use nuclear weapons against Iran in the event of a military conflict.
As far as the West is concerned, Khamenei’s alleged fatwa clearly has not erased fears that Iran is seeking nuclear weapons.
But Vali Nasr, a former senior adviser at the U.S. State Department, says Khamenei's public stance against nuclear weapons is significant in that it can help in negotiations with Tehran.
Nasr says that Turkish Prime Minister Recep Tayyip Erdogan and Foreign Minister Ahmet Davutoglu, who met with Khamenei in March, later told U.S. Secretary of State Hillary Clinton that the supreme leader's public comments could be used as “political leverage” and that Washington shouldn’t miss the opportunity.
“When Erdogan and Davutoglu met with Khamenei in March, they got an earful about [his nuclear stance]. You can take it any which way you want. You could think that they’re practicing dissimulation, or hiding their true intent, which could be said about any political position; or you could assume that the Iranians were sending a very clear signal that they were going to meet [U.S. President Barack] Obama’s red line [of weaponization]," Nasr said at an April 16 event at Washington's Carnegie Endowment for International Peace.
On April 1, Clinton called on Iran to substantiate its forswearal of nuclear weapons. She said Tehran's policy could be demonstrated in a number of ways, including shipping out some of Iran’s enriched uranium in exchange for fuel for its research reactor and opening up its nuclear facilities to inspectors.
European Union diplomats who took part in last weekend's nuclear talks in Istanbul have said that Khamenei's fatwa was mentioned by the Iranian delegation.
The diplomats likely offered the same response as Clinton: Prove it.
-- Golnaz Esfandiari