Six world powers are to open their first talks with Iran in more than a year on Monday, hoping the meeting will lead to new negotiations over a nuclear programme the West believes is aimed at making atom bombs.

However, on the eve of their meeting in Geneva, Iran hailed the step as a major step forward in its nuclear work, signalling 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 -- played down expectations of a major breakthrough during the 6-7 Dec discussions. Diplomats say they would view, as a sign of progress, an agreement to meet again for more substantial talks, perhaps early next year.

"All I can tell you is that it's going to be very, very boring," said a senior EU diplomat involved in the talks.

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.

For his part, Iranian President Mahmoud Ahmadinejad has repeatedly said this key issue will not be discussed in Geneva. "Iran's nuclear issue has been resolved. It is not on the agenda and any problem regarding our nuclear activities should be discussed at the IAEA (International Atomic Energy Agency)," said one Iranian official, speaking from Tehran.

Asked upon his arrival in Geneva whether he was optimistic about the meeting, Iranian nuclear negotiator Saeed Jalili said: "Everything depends on the other party's attitude."

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.

The United States has warned of more pressure and isolation if Tehran continues its uranium enrichment activities. Washington says all options, including military, remain on the table and Iran's arch enemy Israel has also not ruled out a military strike if diplomatic efforts fail.

But Iran sought to exploit differences between the six powers, with its ambassador in Beijing saying Tehran would always be a reliable oil exporter to China, praising their bilateral relations as fantastic.

In the meantime, Iran's hardline rulers, seeking to rally nationalist support and distract attention from economic woes, remain defiant.

On Sunday, Iran's nuclear energy chief Ali Akbar Salehi said Iran would use domestically produced uranium concentrates, known as yellowcake, for the first time at a key nuclear facility, cutting reliance on imports of the ingredient for nuclear fuel.

The timing of the announcement appeared aimed at showing Tehran's determination to pursue its nuclear plans before talks with the powers, whose negotiating team will be headed by European Union foreign policy chief Catherine Ashton.

Last week's killing of an Iranian nuclear scientist in Tehran, which Iran has blamed on Western intelligence services keen to impede its nuclear advances, could cloud the atmosphere for dialogue in Geneva.

Iran wants UN sanctions lifted, calling them illegal, and has accused the UN nuclear watchdog in Vienna of sending spies of foreign intelligence services to the country among inspectors who regularly visit its nuclear facilities.