Mottaki told reporters that Tehran would on Monday hand to the UN atomic agency its response to questions raised by the Vienna group - the United States, Russia and France - on the fuel swap deal.
"Tomorrow this ... letter will be conveyed to the IAEA (the International Atomic Energy Agency) in Vienna and then we can immediately start negotiations for the details of exchanging of the fuel," he said in English. "All the details on how that exchange should take place will come out through the discussions and talks in Vienna."
Under the deal, brokered by Turkey and Brazil in May, Iran agreed to send 1,200 kilograms of its low-enriched uranium (LEU) to Turkey to be supplied at a later date with high-enriched uranium by Russia and France.
But it was immediately cold-shouldered by world powers, which backed a fourth round of sanctions against Iran on June 9 over its refusal to halt its sensitive uranium enrichment program.
The Vienna group expressed reservations and raised several questions regarding the deal, but said they were nonetheless ready to talk to Iran to clear up the doubts.
Mottaki, who was speaking after talks with his Turkish and Brazilian counterparts Ahmet Davutoglu and Celso Amorim, said Iran would like to see both of these countries take part in the talks, but said it was not a condition.
Earlier Sunday, Davutoglu had said that Turkey and Brazil were ready to contribute to the talks only if they were invited by all the parties concerned.
Mottaki gave few details on the response Iran would hand to the IAEA on Monday, saying that it would contain Iran's "own views and what we will talk about in Vienna."
Earlier Sunday, President Mahmoud Ahmadinejad said Iran would react swiftly if its commercial shipping or aviation were subjected to inspection.
A UN Security Council resolution on June 9 imposed restrictions on Iranian shipping and other sectors to try to persuade Tehran to curb its enrichment activities. Under the latest sanctions, countries would have the authority to inspect cargo ships heading to or from Iran.
"You should know whoever takes a decision against the Iranian nation, such as the so-called inspection of the Iranian ships or so-and-so toward its aircraft, will immediately receive Iran's reaction," told a conference in a speech broadcast live on radio.
Earlier this month, the European Union banned more planes operated by Iran Air from flying into the airspace of the 27-country bloc on safety grounds. It denied reports there was a ban on Iranian commercial airliners refueling in Germany and Britain as a result of US sanctions. However, some oil companies have stopped jet fuel supplies to Iranian aircraft outside Iran.
Meanwhile, a former CIA director says military action against Iran now seems more likely because no matter what the US does diplomatically, Tehran keeps pushing ahead with its suspected nuclear program.
Michael Hayden, a CIA chief under President George W. Bush, says that during his tenure a strike was "way down the list" of options. But he told CNN's "State of the Union" that such action now "seems inexorable."
He predicted Iran will build its program to the point where it's just below having an actual weapon. Hayden said that would be as destabilizing to the region as the real thing.
US officials have said military action remains an option if sanctions fail to deter Iran.
