For the U.S. and Iran, the talks represent more than trying to hammer out a nuclear deal. In style and substance they are an extension of the historic dialogue opened during September's annual U.N. gathering, which included a 15-minute phone conversation between President Barack Obama and Iran's new president, Hassan Rouhani.
The nuclear negotiations have included intensive one-on-one sessions between U.S. and Iranian envoys, offering opportunities to widen contacts and begin the long process of reconciliation after more than three decades of estrangement. For Iran, it also gives Rouhani's government a chance to show skeptical hard-liners that dialogue is possible with Washington without putting the country's Islamic system in peril.
Iranian hard-liners are suspicious of talk of nuclear compromise since Rouhani took office in September, fearing his team will give too much at the negotiating table and not get enough in terms of sanctions relief.
On Wednesday, Iran's supreme leader, Ayatollah Ali Khamenei, said his country would never compromise on "red lines." Since then Tehran has publicly reverted to its original stance — that the six powers must recognize this activity as Iran's right, despite strong opposition by Israel and within the U.S. Congress.
Still, comments from Iranian officials in Geneva indicated that reverting to tough talk on enrichment may be at least partially meant for home consumption.
In Geneva, a senior Iranian negotiator said the Iranian claim to the right to enrich did not need to be explicitly recognized in any initial deal, despite Khamenei's comment, adding that the supreme leader was not planning to intervene in the talks. He did suggest, however, that language on that point remained difficult and that there were other differences.
Work is proceeding on a compromise along the lines of what the Iranian negotiator said — avoiding a direct reference to any country's right to enrich but still giving enough leeway for Iran to accept it, said a diplomat involved in the talks.