Iran's foreign minister on Wednesday said his country would not export its enriched uranium for further processing, brushing aside the latest UN plan aimed at preventing Tehran from potentially building nuclear weapons.
Instead Manochehr Mottaki said Iran would consider a nuclear swap inside Iran as an alternative plan.
The United Nations last month offered a deal to take 70 percent of Iran's low-enriched uranium to reduce its stockpile of material that could be enriched to a higher level, and possibly be used to make nuclear weapons.
That uranium would be returned about a year later as refined fuel rods, which would solve the impasse over its nuclear program. Fuel rods cannot be readily turned into weapons-grade material.
"We will definitely not send our 3.5-percent enriched uranium out of the country," Mottaki told the semiofficial ISNA news agency. "That means a simultaneous fuel swap could be considered inside Iran."
The counterproposal was an indication of Iran's unwillingness to trust the West with its fuel for the time needed to transform it into the more harmless fuel rods.
Mottaki said that Iranian experts were looking at the modified proposal to determine what amounts of uranium should be exchanged for fuel rods.
However it remained unclear what would happen with Iran's uranium, if it would be shipped out of the country as part of the trade or remain inside Iran.
In Washington, State Department spokesman Ian C. Kelly said the US was waiting for Iran to submit its formal response to the International Atomic Energy Agency, or IAEA.
"What was said today doesn't inspire our confidence" that Iran will accept the proposal that was tentatively agreed to in Geneva.
The idea of Tehran shipping uranium for further enrichment was first raised during a landmark meeting with the US and other world powers
'Enrichment in Iran will continue at any price'
Kelly said the US was still consulting with its negotiating partners on a way forward. At some point, he said, the focus would turn to ways of increasing sanctions pressure on Iran, adding, "We're not quite at that point now. But time is short."
Under the UN proposal, Iran would export its uranium which is enriched at less than 5 percent, enough to produce fuel to burn in plants. Enriching uranium to much higher levels can produce weapons-grade material.
In exchange, the Iranian uranium would be further enriched in Russia and then be sent to France. Once there, it would be converted into fuel rods, which would be returned to Iran.
The amount of uranium that would be exported by Iran under the UN plan, about 1.2 tons (1,100 kilograms) of low-enriched uranium, represents about 70 percent of its stockpile. It would have been sent to Russia in one batch by the end of the year, easing concerns the material would be used for a bomb.
Around 2,200 pounds (1,000 kilograms) of low-enriched uranium is needed to produce enough weapons-grade uranium for a single nuclear warhead, according to experts. Iran is believed to have well over that amount of low-enriched uranium in its stockpiles.
But Mottaki's proposal indicated that Iran was open to further negotiation when he dismissed a comment by US Secretary of State Hillary Clinton that the UN plan was its only choice.
"Diplomacy is not all or nothing. Mrs. Clinton's comments that Iran must accept only this proposal is not diplomatic," he said.
The US and its allies see the export process as buying time to reach a compromise with Iran by depriving it of the amount of uranium needed to potentially make a nuclear bomb. Western powers believe Iran is seeking nuclear weapons, or at least the ability to produce them on short notice. Tehran says its uranium activities are aimed only at generating electricity.
IAEA inspectors visited Fordo last month.
The heavily fortified and bunker-like once-secret uranium enrichment facility has further heightened Western suspicions about the extent and intent of Iran's nuclear program.
Soltanieh said that Fordo looked the way it was because uranium enrichment will "not be stopped by military attack, that is the political message of this site."
He added that "the important message is ... enrichment in Iran will continue at any price."
Iran says the facility was fortified to protect against any possible attack by the United States or Israel.
Officials say the plant won't be operational for another 18 months and would produce uranium enrichment levels up to 5 percent, suitable only for peaceful purposes. Weapons-grade material is more than 90 percent enriched.