The reported defection of an Iranian scientist to the United States has renewed speculation about a CIA plot to sabotage Iran's nuclear program through covert action.
But it remains unclear whether Shahram Amiri, the young physics researcher who reportedly joined forces with the US spy agency, represents an intelligence coup for Washington or a minor setback for Tehran, former CIA officers said.
ABC television reported that Amiri, who went missing without explanation in Saudi Arabia last year, had defected and resettled in the United States in cooperation with the Central Intelligence Agency.
Amiri, in his thirties, worked at Tehran's Malek-Ashtar University of Technology, part of a network of research centers with close ties to Iran's powerful Revolutionary Guards and the country's weapons industry.
The scientist did not appear to play a senior role in the country's nuclear project, and his knowledge may have been confined to a single aspect of the program.
"It's really impossible to say how much of a window this kind of a defector could provide without knowing how much he was reading into aspects of the entire program, as opposed to chipping away at one part of the program," CIA veteran Paul Pillar told AFP.
"One ought to be very cautious about how much a difference any one individual might make," said Pillar, now at Georgetown University.
Some media reports suggested the scientist may have helped inform the Americans about a secret enrichment site near Qom, which caused international outrage when it was revealed in September.
Amiri's disappearance appeared to confirm reports in recent years that US intelligence agencies have tried to lure away key civilian and military figures to undercut Iran's nuclear drive in an operation dubbed "Brain Drain."
The fate of a former Iranian deputy defense minister who disappeared in Istanbul in 2007, General Ali Reza Asgari, remains unresolved, amid speculation he defected as well and offered his knowledge of the Revolutionary Guard Corps.
The suspected defections offer a glimpse into a secret struggle between Western intelligence agencies and Iran, with the United States and its allies working to delay Tehran's nuclear project by clandestine means even as they seek international support for tougher sanctions.
"The one thing that we have done, and this has come out in the open press... is to feed faulty components into the supply chain for Iran's nuclear weapons program," said Clare Lopez, who worked for the CIA during and after the Cold War.
Working through a family of Swiss engineers, the CIA reportedly managed to provide Libya and Iran with flawed parts for several years, according to The New York Times and other media.
In 2006, a sabotaged power supply failed at the uranium enrichment plant in Natanz, reportedly causing 50 centrifuges to explode and setting back Tehran's nuclear fuel work.
Former intelligence officers said defections are a delicate, risky business, and it remained uncertain whether Amiri had cooperated with the Americans over a long period of time.
"By and large defections like this are what you call walk-ins, that is they come to you," said Bruce Riedel, a retired CIA officer and fellow at The Brookings Institution think-tank.
"Typically, a response for a walk-in is, 'Hey wait, we rather you stay in place and provide an ongoing stream of intelligence.'"
Iran remains a difficult target for US spies, as Washington has not had an embassy in Tehran for 30 years, cutting off opportunities to develop intelligence sources and contacts.
Moreover, Iran has honed an effective counterintelligence service with "a good track record" of exposing foreign espionage, Riedel said.
Amiri could be a gold mine, offering a trove of information about the nuclear program, which US and European governments insist is a cover for a clandestine nuclear weapons project.
"The other alternative is we're so desperate to gain information on the Iranian nuclear program that we'll take anything we can get," Riedel said.
"I wouldn't be surprised if that was the case."
© AFP 2015