Reports from Vienna this week suggest that already-tense talks over Iran's nuclear program and related sanctions have at times descended into undisguised acrimony.
Self-imposed deadlines have repeatedly been extended, but there is clearly frustration and anger on both sides -- Iran, on the one hand, and Britain, China, France, Russia, and the United States plus Germany, on the other.
One exchange in particular, seemingly based on an unnamed Russian source, has garnered the attention of two Iranian news agencies.
Iran's semiofficial Mehr news agency reported that at a July 6 meeting, Iranian Foreign Minister Mohammad Javad Zarif snapped back at U.S. negotiators who had addressed him in a "threatening tone."
The other agency, Mehr, quoted the unnamed Russian source close to the talks as saying that Zarif responded by shouting at the U.S. team, "You're basically not in a position to decide about our country's missile capability." The same source added that EU foreign policy chief Federica Mogherini reacted by threatening to leave the talks.
Zarif's riposte, as quoted by several Iranian news outlets, was the stuff of legends and memes: "Never threaten an Iranian."
One of the Iranian accounts, by IRNA, quoted Russian Foreign Minister Sergei Lavrov immediately adding, "Nor a Russian."
IRNA also quoted unnamed diplomats citing another spat, this time when U.S. Secretary of State John Kerry and Zarif allegedly shouted at each other so loudly during a recent bilateral meeting in Vienna that they were overheard by people in nearby rooms of the swank Palais Coburg hotel.
Iran's heavily censored state media are often used by its religious and political establishment for propaganda purposes.
Regardless of the accuracy of the reports, which could not be independently verified, Iranians have launched a new hashtag in support of Zarif's message: #NeverThreatenAnIranian.
Some used the hashtag to portray Iran's foreign minister as a hero (or even superhero) standing up to pressure and fighting for Iran's interests while rejecting "excessive" Western demands.
Some noted that the reports appeared to give the already popular Zarif a boost among supporters.
Others posted photos from Iran's brutal crackdown after the disputed presidential vote in 2009, suggesting that the Iranian establishment already does a fine job of threatening Iranians and that no additional help was needed.
"Never threaten an Iranian. Why? Because we take care of it inside the country," tweeted this user.
EU and Iranian officials meanwhile appeared to dismiss the reports of the spat:
But depending on the outcome of the negotiations and probably irrespective of its veracity, the Zarif (and Lavrov) "never threaten" remarks could provide subsequent narratives on either side with a defining moment.