GENEVA, Oct 16 (Reuters) - If world powers were looking for signs that Iran is serious about reaching a deal on its disputed nuclear programme, the fact that its foreign minister took part in negotiations in Geneva this week with debilitating back pain was a clear one.
In one of the most striking images of two days of protracted negotiations, Iranian Foreign Minister Mohammad Javad Zarif entered a news conference on Wednesday in a wheelchair, after a back and leg injury last week left him unable to stand or walk without intense discomfort.
"I'm really in pain," Zarif told Reuters on Tuesday, as he returned to his hotel from the first session of talks.
His predicament elicited empathy from those on the opposite side of the negotiating table, in a sign of how relations between diplomats have improved under new Iranian President Hassan Rouhani, who has pledged to end Tehran's international isolation.
"There isn't one among us who doesn't have a back problem," a senior U.S. administration official said.
"Everyone had a back story for him, books they thought he should read, things he might try, because we all have suffered."
Zarif, 53, told negotiators he had acupuncture to alleviate the pain, the U.S. official added.
It was just one detail in two days of talks that indicated a new tone in dealings between the two sides, although officials cautioned that the gap in substance remained wide.
But such scenes would have been unimaginable just a few years ago when U.S. and Iranian officials would go to great lengths to avoid direct contact.
Iran and six world powers - the United States, Britain, France, Russia, China, and Germany, known collectively as the P5+1 - are engaged in negotiations to try to close a diplomatic deal on Iran's nuclear program. The United States and its allies suspect Iran is working towards a nuclear weapons capability, and have imposed punishing economic sanctions to convince Iran to curb the programme.
Iran insists its programme is purely peaceful, and Rouhani and Zarif have sought better relations with the West in an effort to win a lifting of the sanctions.
Zarif injured his back last week, he wrote on his Facebook page, after reading a report in a hardline Iranian newspaper that he said had misquoted him about bilateral contacts between Tehran and Washington.
Iranian media published a picture of Zarif meeting reporters on the plane ride from Tehran to Geneva while lying on a couch, covered with a blanket and with a laptop resting on his stomach.
Both sides said after this week's talks that they were encouraged by the other's approach to the meeting in Geneva, saying the level of detail discussed was unprecedented.
In another sign of Iran's readiness for substantive progress, the talks were conducted in English for the first time, cutting down on translation time and making for a smoother discussion, Western officials said.
Saeed Jalili, the hardline war veteran who had led previous rounds of negotiations, spoke at the talks and in news briefings in Persian. Western officials complained that his statements were long-winded lectures on Iran's grievances with the West.
"The pace of the discussions is much better and creates the ability to really have the kind of back-and-forth one must have if you want to have a negotiation," the U.S. official said.
Another Western official said: "As part of the new climate, we could exchange in English ... This is more than a detail." (Additional reporting by Stephanie Nebehay in Geneva; Editing by Giles Elgood)