Iran appeared flexible enough at talks with six major powers to mute calls for immediate tougher sanctions, but signalled no retreat from nuclear goals it says are only to produce energy and not bombs.
Western officials said Iran had agreed in principle at the October 1 meeting in Geneva to a deal under which it would send most of its enriched uranium to Russia for further processing.
France would then place the uranium in fuel assemblies which Iran would use, under safeguards, in a Tehran nuclear reactor which produces medical isotopes but is running low on fuel.
A senior US official in Geneva said that the deal could calm tension by reducing Iran's stockpile of low-enriched uranium.
He called it a "positive interim step to help build confidence so that we'd have more diplomatic space to pursue Iran's compliance with its obligations... and to tackle the more fundamental question of Iran's nuclear programme".
But a senior Iranian official said the deal was preliminary and contested reports that Iran was ready to send 1.2 tonnes of its 1.5-tonne low-enriched uranium stockpile abroad for refining to the 20 percent purity needed for the Tehran reactor.
"Whatever they've agreed [in Geneva] on 20 percent enrichment is just based on principles," the official said. "We have not agreed on any amount or any numbers."
The degree of Iranian commitment to the proposal, which will be discussed at the International Atomic Energy Agency (IAEA) in Vienna on October 18, remains unclear, but one expert said there was no way Iran would renounce its uranium enrichment work.
"I cannot see in any conceivable agreement that the Iranians would give up their ambitions to perfect the technology for future power reactors within Iran," said Paul Ingram, director of the British American Security Information Council.
"The Iranians are playing for time in a very complex game," he added. "It involves firing missiles at inopportune times in order to appear strong and then quietly trying to draw the sting from any significant move for sanctions."
Iran conducted missile tests earlier last week, just days after declaring the existence of a second uranium enrichment facility carved into a mountainside near the city of Qom.The admission, which diplomats said Iran made only after it realised that Western intelligence agencies knew of the plant, sparked an international furore over Iranian nuclear activity.
Tehran, which denies it broke rules by not declaring the site before, says it will open it soon to the IAEA, whose chief, Mohamed El Baradei, was due in the Iranian capital last week.
Swift access for IAEA inspectors - Washington and Paris have set a two-week deadline - will provide a degree of reassurance, but will not douse Western concerns, Ingram said.
"There will be many in the West looking to discover other parts of the nuclear fuel cycle because there is a very strong suspicion this is just the tip of the iceberg," he added.
Iran has accused Western powers of bullying and double standards in pushing to curtail its nuclear programme.
Mutual mistrust remains high, but both sides portrayed the meeting in Geneva, which included the highest-level US-Iranian exchange in 30 years, in cautiously positive terms.
US president Barack Obama called it a "constructive beginning", but added: "Our patience is not unlimited."
If the negotiations that began in Geneva stall, like so many before them, the US and its European allies will seek to impose harsher sanctions on Iran, but are likely once again to find Russia and China reluctant to endorse such measures.
More talks with the six powers - Britain, China, France, Germany, Russia and the US - are planned for later this month. Iran insists its right to enrich uranium is not negotiable, despite Security Council demands that it halt such work.
Meanwhile, Tehran wants to discuss wide-ranging security issues instead.
Ingram argued that it was unrealistic to expect a deal on Iran's nuclear programme in isolation from wider concerns.
"It plays into the hands of the Iranian regime because they have full domestic support for the nuclear programme," he said.
US-Iranian engagement that included a host of other issues, ranging from efforts to stabilise Iran's neighbours Iraq and Afghanistan to Tehran's ties with the militant Hamas and Hezbollah groups, might prove more productive, Ingram said.
"There would be more common ground because regional security and stability is in the interests of Iran and the US and there would also be more scope for negotiation and deals."For all the latest business news from the UAE and Gulf countries, follow us on Twitter and Linkedin, like us on Facebook and subscribe to our YouTube page, which is updated daily.
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