Iran would negotiate on halting higher-grade uranium enrichment if given fuel for a research reactor, senior officials said, reviving a previous offer in a possible attempt to show flexibility in stalled nuclear talks with world powers.

The talks have made scant progress since resuming in April, leading to harsher Western sanctions against Iran and increasing talk of Israeli air strikes on its arch-adversary over concerns Tehran is covertly seeking the means to develop nuclear weapons.

The Islamic Republic's economy is suffering from the tightened noose of sanctions, with the rial currency losing nearly two-thirds of its value to the dollar over the past year.

"If a guarantee is provided to supply the 20 percent (enriched) fuel for the Tehran Research Reactor, our officials are ready to enter talks about 20 percent enrichment," Foreign Ministry spokesman Ramin Mehmanparast said at a Eurasian media forum in Kazakhstan on Friday, according to Iran's Press TV.

Foreign Minister Ali Akbar Salehi told the German newsmagazine Der Spiegel earlier in the week: "If our right to enrichment is recognized, we are prepared to offer an exchange. We would voluntarily limit the extent of our enrichment program, but in return we would need a guaranteed supply of the relevant fuels from abroad."

At the heart of Iran's dispute with world powers is its insistence on the right to enrich uranium and that economic sanctions should be lifted before it stops activities that could lead to its achieving the capability to produce nuclear weapons.

The United States and European allies reject such conditions. They say Iran forfeited a right to enrich by having concealed sensitive nuclear work from UN inspectors and blocking their inquiry into suspected bomb research.

They also believe that dropping sanctions first would remove any incentive for Iran to come clean and negotiate seriously.

Mehmanparast, the Foreign Ministry spokesman, spoke on the same day the European Union provisionally approved yet wider economic sanctions complementing U.S. plans for further financial penalties.

Mehmanparast said any flexibility shown by Iran should be matched by reciprocal measures from world powers, including full recognition of Iran's right to enrich uranium, according to Saturday's Press TV report.

There is no sign Iran's readiness to discuss its enrichment of uranium to a fissile concentration of 20 percent would go anywhere near enough to satisfy the demands of the West.

World powers want Iran to stop 20 percent enrichment, shut down the Fordow underground centrifuge plant where this work is carried out and ship out its stockpile of this material.

Western officials say such gestures would serve to raise confidence in Iranian intentions but more would be needed to obtain any significant relief from sanctions.

Iran says it needs uranium enriched to a fissile purity of 20 percent for a medical research reactor in Tehran, but this would also overcome most of the hurdles in terms of technology and time to the 90 percent level suitable for nuclear weapons.

According to the latest International Atomic Energy Agency watchdog report, issued in August, Iran has a stockpile of 20 percent uranium of just over 90 kilograms (200 pounds).

Traditionally experts say 200-250 kg would be required for one nuclear device, if it is refined further to weapons grade, but some say less would do. Iran is believed to be producing about 15 kg per month.

A U.S.-based think tank earlier this week said Iran would currently need at least two to four months to refine enough uranium for one bomb but that considerably more time would be required to assemble a deliverable nuclear weapon.