The report quoted an unnamed informed source as saying Iran proposes some "modifications" in the draft of the UN-brokered plan but has accepted the overall framework, in what will be Tehran's "final response."

A top aide of US President Barack Obama, meanwhile, indicated Washington would push for new sanctions against Tehran if it faltered on its commitments regarding its nuclear programme.

But a top Moscow official, whose country has veto power in the UN Security Council, said this was "unlikely" in the near future.

Mehr said Tehran's envoy to the International Atomic Energy Agency, Ali Asghar Soltaniheh, will meet IAEA chief Mohamed ElBaradei in the Austrian capital on Thursday and "give Iran's response to the Vienna talks."

The IAEA brokered the deal during the Vienna talks earlier this month which envisages Iran shipping out its low-enriched uranium (LEU) abroad for converting into fuel for a Tehran reactor.

An influential Iranian lawmaker said the country's Supreme National Security Council (SNSC) -- the top national security decision making body -- will later Wednesday put the finishing touches to Tehran's official response.

"The council will decide on Wednesday its position about the response to the agency's proposal on supply of fuel to Tehran reactor," Alaeddin Borujerdi told the ISNA news agency.

Borujerdi, head of parliament's committee on national security and foreign policy, advocates that Iran's LEU be sent abroad gradually and not all in one shot.

Iranian state media had said on Tuesday that Tehran wanted "very important changes" in the deal arranged by the IAEA.

France says the deal calls for Tehran to export to Russia more than 1,200 kilos (2,640 pounds) of its 3.5 percent LEU for refining up to 20 percent purity to fuel the Tehran reactor that makes medical isotopes.

World powers back this, as they fear Iran intends to enrich its LEU to even higher levels for use in atomic weapons. Another plus from their perspective is that the Tehran facility is closely monitored by the IAEA.

Tehran says its enrichment drive -- the most controversial aspect of its nuclear project -- is peaceful. Enriched uranium can be used to power nuclear reactors as well as to make the fissile core of an atom bomb.

Iran was to offer its response to the deal by last Friday but delayed it amid conflicting views on it from its senior officials who are largely of the opinion that Tehran must transport its LEU in batches rather than all at once.

EU foreign policy chief Javier Solana, who has been West's negotiator with Tehran, was expected to speak to Iranian officials later on Wednesday regarding the deal.

On Tuesday, he said the IAEA-drafted plan was a "good deal."

"I don't think this requires fundamental changes," he said, referring to reports Tehran would seek major changes to the deal.

Since 2006, Solana has been negotiating on behalf of world powers to try to persuade Iran to enter talks on suspending enrichment work in exchange for political and economic benefits.

Iran is already under three sets of UN sanctions for enriching uranium at its Natanz plant.

The United States is prepared to respond if Iran does not abide by its commitments over the controversial nuclear programme, a top aide to Obama said.

"Nothing is off the table," National Security Adviser James Jones said on Tuesday, raising the possibility that Washington could go for new sanctions if current diplomatic efforts fail.

"We will see if engagement is able to produce the concrete results we need, and we'll be prepared if it does not."

But Sergei Prikhodko, a top aide to Russian President Dmitry Medvedev, said on Wednesday that further sanctions are "unlikely in the near future."

Moscow has been indicating in recent weeks it could support Washington on sanctions against Tehran if diplomatic efforts failed.