The United States on Thursday said it is awaiting a "formal response" from Iran to a UN-drafted plan that calls for Tehran to ship much of its uranium abroad for enrichment, French news agency AFP quoted a State Department spokesman as saying.

"We need to hear a formal response from Iran," spokesman Ian Kelly said, hours after the International Atomic Energy Agency said it had received a response from Tehran without giving any details of its contents.

"We'll see what kind of clarifications we get from the Iranians," Kelly said.

Kelly added there was "complete unity among the four parties" - the IAEA, the United States, Russia and France - that are negotiating with Iran.

Iran had given an initial response to the plan, the IAEA said Thursday.

The wording of the statement by the United Nations nuclear watchdog appeared to dash Western hopes of a quick deal that would delay Tehran's ability to make a nuclear weapon.

The U.S. and allied countries were seeking Iranian agreement to ship out 70 percent of its low-enriched uranium to Russia in one shipment for further enrichment and conversion into fuel for a Tehran research reactor.

Sending that amount in one batch would not leave Tehran with enough material to make weapons-grade uranium should it decide to make a warhead. Experts say Iran would need at least a year to produce enough to make up for the exported material, giving the international community a window in its efforts to persuade the Islamic Republic to freeze its enrichment program.

But Iran has signaled in recent days that it was unwilling to give up most of its enriched stockpile in a single shipment and would seek to re-negotiate terms worked out by IAEA chief Mohamed ElBaradei in talks last week with Iran, Russia, France and the U.S. That Iranian stance was reinforced by the language of the IAEA statement.

Besides speaking of an initial response from the Iranian authorities - suggesting that Iran was looking for further talks - the statement indicated the possible need for further negotiations. It said ElBaradei expressed hope that agreement can be reached soon and was consulting with the four nations involved.

The plan would commit Iran to turn over more than 2,600 pounds of low-enriched uranium - more than the commonly accepted amount of low-enriched uranium needed to produce weapons-grade uranium. The West says Tehran agreed in principle to export that amount in one shipment during Oct. 1 talks in Geneva with the U.S. and five other world powers.

But if Tehran did accept the plan in Geneva, it has subsequently backtracked.

The Islamic Republic has indicated that it may insist on being allowed to buy the fuel for the Tehran reactor from abroad - or to ship the material in small batches. That would not reduce fears about further enrichment to weapons-grade uranium because Iran would be able to quickly replace small amounts it sent out of the country with newly enriched material.

A pro-government newspaper said Thursday that Iran would seek major revisions to the proposed deal, including shipping abroad its low-enriched uranium (LEU) in stages rather than all at once.

Without giving a source, the newspaper Javan also said Iran wanted a "simultaneous exchange", receiving higher-enriched uranium to run a Tehran research reactor at the same time as it ships LEU abroad for conversion into fuel for the same purpose.

Meanwhile, Israel on Thursday blasted the uranium exchange deal with Iran as one that would only delay by one year Tehran's alleged progress toward a nuclear weapon.

Defense Minister Ehud Barak said the downside of the agreement was that it granted international recognition to uranium enrichment by Iran.

He urged the international community to go further and demand a complete stop to enrichment on Iranian soil.

"If this agreement is implemented, it will take them back a year, but there is a fly in the ointment. It means that they [the U.S., Russia and France] recognize that Iran is enriching uranium and that helps them [Iran] with their argument that they are enriching uranium for peaceful purposes," Barak said.

"It is important to insist on an end to enrichment in Iran," he told Israel Radio.

Iran wants two amendments to nuclear draft

Iranian President Mahmoud Ahmadinejad said earlier Thursday that Iran would not retreat "one iota" on its nuclear rights, but it is ready to cooperate on issues regarding atomic fuel, power plants and nuclear technology.

He said the provision of nuclear fuel for a Tehran research reactor was an opportunity for Iran to evaluate the "honesty" of world powers and the United Nations nuclear agency.

"We welcome the uranium exchange deal and are ready for cooperation, but the countries involved in the deal should also fulfil their commitments," Ahmadinejad said in a speech in Mashad in north-eastern Iran that was broadcast on television.

According to Iranian media, Tehran has accepted the framework of the deal, but has demanded changes to it.

Two such reported changes to the deal, according to the media sources, included the gradual shipment of its low-enriched uranium (LEU) abroad rather than sending it in one go, a pro-government newspaper reported on Thursday.

It also said Tehran wanted a "simultaneous exchange," under which it would receive fuel for a Tehran research reactor at the same time as it ships LEU out of the country, Javan newspaper reported, without giving a source.

Ahmadinejad on Thursday also called on the United States to drop its support for Israel to prove its claim of wanting change.

"You have to choose between your prestige in the world or support for the Zionist regime - Israel," Ahmadinejad said in a speech in Mashad in north-eastern Iran that was broadcast on television. "You have to chose one of the two options."

IAEA inspectors return from visit to enrichment site

Earlier Thursday, a team of UN nuclear inspectors returned from a visit to a previously secret Iranian uranium enrichment site, with their leader expressing satisfaction with the mission.

What the inspectors saw - and how freely they were allowed to work - will be key in deciding whether the world powers seek a new round of talks with Tehran.

The Fordo site is near the holy city of Qom. Iran revealed it was building it September 21 in a confidential letter to the International Atomic Energy Agency. Just days later, the leaders of the U.S., Britain and France condemned Tehran for having kept it secret.

The West believes Iran revealed the site's existence only because it had learned that the U.S. and its allies were about to make it public. Iran denies that.

Tehran says it wants to enrich only to make nuclear fuel. But the West worries that Iran wants to create fissile warhead material.

"We had a good trip," said Herman Nackaerts, who headed the International Atomic Energy Agency inspection team.