Iran resumed negotiations with six world powers on Tuesday after a six-month hiatus, under pressure to propose scaling back its disputed nuclear program to win relief from crippling sanctions.
The two-day meeting, the first since relative moderate Hassan Rouhani was elected Iran's president on a platform to ease its international isolation, is seen as the best chance in years to defuse a long stand-off over Iran's nuclear ambitions that has heightened the risk of a new Middle East war.
In a possible sign of the Islamic Republic's determination to engage meaningfully, the talks in Geneva were expected to be held in English for the first time, said a senior U.S. State Department official, who asked not to be named.
On the eve of the talks, Washington held out the prospect of quick sanctions relief if Tehran moves swiftly to allay concerns about its nuclear program, although both countries said any deal would be complex and take time.
Western diplomats said it remained unclear whether proposals for ending the dispute that Iran promised to put forward in the meeting would be sufficient to enable headway to be made.
Western powers suspect Iran is trying to develop the means to make nuclear weapons behind the screen of a declared civilian atomic energy program. Tehran denies this but its refusal to curb sensitive nuclear activity or permit unfettered U.N. inspections has drawn tough international sanctions.
"We definitely hope that the new momentum will translate into some concrete step forward," a senior Western diplomat said ahead of the talks. But Iranian atomic energy chief Ali Akbar Salehi suggested this week's talks may not get that specific.
Asked whether Iran's Fordow underground uranium enrichment site, which the big powers want shut, would be discussed, Salehi was quoted as saying by the Fars News Agency: "We do not expect to get into contents in today's meeting because the discussion will be on the generalities and I believe that the principles, timing and initiating the process will be considered."