Iran is studying proposals from the United States, Russia and France on a nuclear fuel swap, an Iranian news agency reported on Monday, but Paris said the only valid offer was an existing deal that Tehran has yet to accept.

The semi-official ILNA news agency quoted Ali Akbar Salehi, the head of Iran's Atomic Energy organization, as saying proposals had been received after Tehran opted to step up its own uranium enrichment, a decision it announced last week.

After Iran's decision to internally produce 20 percent enriched uranium, we received some proposals from Russia, America and France and right now we are studying this issue along with other proposals from different countries, the agency quoted him as saying.

Washington and its allies fear Iran wants to acquire nuclear weapons, and are lobbying for new United Nations sanctions, but Tehran says its aims are purely peaceful.

In Paris the French Foreign Ministry said the sole valid offer was a deal presented last year by the U.N.'s International Atomic Energy Agency (IAEA). Mr. Salehi should know that the only proposition is the one put forward by the IAEA last October, which has still not received a satisfactory response, said ministry spokesman Bernard Valero.

Iran originally accepted a plan to send 75 percent of its low-enriched uranium (LEU) to Russia and France, where it would be converted into special fuel for a Tehran reactor that makes isotopes for treatment of cancer patients. For big powers, the key point of the plan was to reduce Iran's LEU reserve below the quantity needed for a nuclear bomb, if enriched to a high level.

But Iran later said it wanted fresh fuel for the reactor before it would agree to ship any enriched uranium stocks to Russia and France, and then only in small, gradual amounts.

CONTRADICTORY REMARKS

Iranian Foreign Ministry spokesman Ramin Mehmanparast also appeared to contradict Salehi's remarks. Tehran was ready to swap fuel only if its conditions were observed, he said.

Since we have not received any new proposals until now, domestically producing this fuel is on the agenda, ILNA quoted him as saying.

Iran will continue to produce 20 percent uranium until it meets its research reactor needs and at the moment doesn't have any intention to limit itself to particular methods, he added.

President Mahmoud Ahmadinejad said last Thursday that Iran was now able to enrich uranium to more than 80 percent purity, close to levels experts say would be needed for a nuclear bomb, although he denied it had any such intention.

Iran and the five permanent members of the United Nations Security Council plus Germany have so far failed to agree on terms for swapping uranium for enrichment outside Iran.

These countries' proposal will only stop Iran from enrichment when all our terms and conditions for swapping enriched uranium are observed, Salehi said.

U.S. Secretary of State Hillary Clinton said on Sunday she saw few alternatives to more sanctions on Iran. Washington sought a peaceful end to the standoff but did not want to engage diplomatically while they are building their bomb, she added.

A new round of U.N. sanctions would require the consent of veto-wielding Security Council members Russia and China, both of which have been less inclined to impose them in the past.

(Reporting by Ramin Mostafavi, additional reporting by Crispian Balmer in Paris, writing by Andrew Hammond; editing by David Stamp)