A worker in the fuel manufacturing plant at the Isfahan uranium conversion facility 440 kilometres south of Tehran. (Caren Firouz/Reuters)

Iran says it would back off plans to enrich its stockpile of uranium if the West provides nuclear fuel needed for its research reactor.

The latest offer by Iranian officials comes after the western Asian country notified the United Nations on Monday that it intends to start enriching its uranium to 20 per cent on Tuesday, to refine its uranium stockpile to a higher purity to operate a medical research reactor in Tehran.

Monday's announcement angered Western powers, who have long been calling on Iran to give up its nuclear enrichment program, which they fear could be used to create weapons-grade uranium enriched to 90 per cent.

Members of the UN, including France and the United States, called Monday for a new round of sanctions against Iran.

Iranian Foreign Ministry spokesman Ramin Mehmanparast told reporters Tuesday that any further enrichment would be done with the co-operation and supervision of the UN nuclear watchdog, adding that "if other countries or the agency could provide the fuel, our attitude can be different as well."

The head of Iran's nuclear agency, Ali Akbar Salehi, told state TV late Monday that Iran was willing to back off from the plan, provided the UN came through with the moderately enriched uranium it needs.

U.S. urges sanctions in 'weeks, not months'

French Foreign Minister Bernard Kouchner accused Iran of "blackmail," according to media reports Monday. U.S. Defence Secretary Robert Gates told reporters the UN should seek new sanctions against Iran in "weeks, not months."

China, which has been more supportive of Iran than other members of the UN Security Council, refused to comment on the call for sanctions Tuesday, instead calling for a resumption of talks. "I hope the relevant parties will step up efforts and push for progress in the dialogue and negotiations," said Chinese Foreign Ministry spokesperson Ma Zhaoxu.

The UN's atomic agency had drawn up an agreement last year whereby Iran would get nuclear fuel for its reactors, but only after it gave up its stockpile of uranium to Russia for conversion into fuel that could not be used for weapons. Iran balked at this, and made a counterproposal to purchase the fuel but keep its stockpile.

The negotiations began after Iran revealed it had begun work on a second uranium enrichment plant, one that nuclear regulators knew nothing about and in violation of UN resolutions. Iran eventually allowed investigators to visit the site.

The UN has already imposed three sets of sanctions aimed at pressuring Iran to freeze enrichment, but Iran has instead steadily expanded its program.

With files from The Associated Press