On the eve of the meeting in Geneva, Iran announced what it called a major step forward in its nuclear work, signaling it is not about to back down in a long-running battle over what it insists are peaceful plans for energy production.

The six powers - Britain, China, France, Germany, Russia and the United States - do not expect a major breakthrough during the Dec 6-7 discussions. Diplomats say they would view as a sign of progress an agreement to meet again for more substantial talks, perhaps early next year.

Western powers want Iran to suspend uranium enrichment activity, which can produce fuel for nuclear power reactors or provide material for bombs if refined to a higher degree.

However, Iranian President Mahmoud Ahmadinejad has said this key issue will not be discussed in Geneva. Before the talks, US National Security Council spokesman Mike Hammer said Washington and its allies were looking to see if Iran would enter into discussions "with the seriousness of purpose required to begin to address international concerns with its nuclear programme."

The West has tightened sanctions on Iran in recent months, and Western diplomats say these are hurting Iran's oil-dependent economy, which Tehran denies.