)
The two-day meeting in the Kazakh city of Almaty comes as sanctions bite against the Islamic republic and Israel still refuses to rule out air strikes to knock out Iran's suspected nuclear weapons drive.
The world powers will offer Iran permission to resume its gold and precious metals trade as well some international banking activity which are currently under sanctions, Western sources close to the negotiations told AFP.
But in exchange, Iran will have to limit sensitive uranium enrichment operations that the world powers fear could be used to make a nuclear bomb, the sources added.
The first round of closed-door talks started at around 1400 IST under high security at the Rixos hotel in this Kazakh city under the shadow of the Tien Shan mountains, a Western official said, adding it was not clear how long the first session would last.
Little apparent progress has been made since the last such talks in Moscow in June 2012 ended without any breakthrough and Iranian officials have insisted they will offer no special concessions at the two-day talks.
"We have prepared a good and updated offer for the talks, which we believe is balanced and a fair basis for constructive talks," said Michael Mann, the spokesman for EU foreign policy chief Catherine Ashton.
"The offer addresses international concerns... On the nature of the Iranian nuclear programme, but is also responsive to Iranian ideas," he said.
A Western official involved in the negotiations said the offer would still insist Iran stop enriching uranium to 20% and shuts down its controversial Fordo plant where such activity occurs.
But Iran denies it is developing nuclear weapons and wants the world to respect its international "right to enrich" uranium -- something current UN sanctions say it cannot do because of its refusal to cooperate with nuclear inspectors.
In a sign of the tough negotiations ahead, a source in the Iranian delegation said the issue of 20% enrichment was not a subject his country was ready to discuss at this stage.
"We don't expect any breakthrough. The Iranians have made different declarations in the last days. It depends if you take the positive or the negative ones," said one Western official who asked not to be identified.
World powers are represented at the table by the five permanent UN Security Council members and Germany -- the so-called P5+1 -- with the Iranian team headed by top nuclear negotiator Saeed Jalili.
