By Fredrik Dahl
VIENNA (Reuters) - Would Israel discreetly warn U.N. nuclear chief Yukiya Amano so that he could withdraw his inspectors before any air raid on Iran, as the United States did in a dramatic night-time phone call to his predecessor just before the 2003 war in Iraq?
With persistent speculation that Israel might soon attack Iran's nuclear sites and his own increasingly tense relations with Tehran, the potential dangers facing Amano's staff on the ground are likely a big worry for the veteran Japanese diplomat.
If unlucky, they run the risk of being at a site targeted by Israeli missiles and may also face Iranian anger and likely expulsion afterwards. Their departure would greatly diminish the world's knowledge about the Islamic state's nuclear programme.
The U.N. atomic agency could face an "acute dilemma" as it is obliged to continue to carry out its inspection mandate in Iran while also protecting its personnel from harm, disarmament and non-proliferation expert Trevor Findlay said.
"It also must be careful not to be seen to be facilitating an Israeli attack by withdrawing its staff in anticipation, either after an Israeli warning or simply by guessing when Israel might attack," said Findlay, of Harvard University's Belfer Center for Science and International Affairs.
Iranian officials have stepped up their criticism of the U.N. International Atomic Energy Agency (IAEA), saying it might have been infiltrated by "terrorists" and accusing it of passing nuclear secrets to Israel.
Though dismissed by Western diplomats as a way to distract attention from mounting suspicions about Iran's nuclear aims, such allegations are likely to increase concern at the IAEA's Vienna headquarters about the inspectors' safety.
The IAEA is believed to have experts constantly deployed in Iran, providing a unique insight into its nuclear advances.
While there may only be a few of them at any given time, they are tasked with inspecting uranium enrichment sites that would be prime targets in any military onslaught. Their exact numbers, schedule and whereabouts are kept secret.
"The risk to IAEA inspectors if they are present on a nuclear site when it is undergoing an air strike is obvious," Pierre Goldschmidt, a former chief U.N. nuclear inspector, said.
"I can only speculate that Israel would indeed warn the IAEA beforehand as the Americans did before the Iraq war in March 2003," he said, referring to a U.S. envoy's call to Mohamed ElBaradei, who headed the IAEA at the time.
But this could also alert Iran, and Israel would likely want to keep its operation secret as long as possible, in contrast to a well-publicized U.S. military buildup in the Gulf in preparation for the invasion of Iraq.
Israel, believed to have the Middle East's only atomic arsenal, sees a nuclear-armed Iran as a threat to its existence and, frustrated by the failure of diplomacy and sanctions to rein in Tehran's nuclear activity, has ramped up threats to attack its arch-enemy. Iran says it is enriching uranium only for peaceful energy purposes, not for nuclear bombs.
"Logic dictates that when you launch a military action, you don't announce it in advance, because then you lose any element of surprise," Uzi Eilam, a retired Israeli brigadier-general and a former director of the Israel Atomic Energy Commission, said.
Israel would have to consider that if "they informed the IAEA of their plans, a subsequent exodus of IAEA personnel from Iran might signal to Iran that an attack was imminent," nuclear proliferation expert Mark Hibbs said.
Eilam suggested, however, that Israel might time any strike with the safety of inspectors in mind. He said Israel chose a Sunday to bomb an Iraqi reactor in 1981 to make it less likely that French engineers still working there would be hit.
The IAEA carries out regular inspections of 16 declared nuclear facilities in Iran, including likely Israeli targets such as the underground Natanz and Fordow enrichment plants.
Scheduled visits take place in daytime during regular work hours, former IAEA Deputy Director General Olli Heinonen said. But there are also "unannounced inspections" at Natanz and Fordow of about 1-2 days per month, he said.
Refined uranium can be used to fuel power plants but also provide the explosive core of a bomb if processed further.
The IAEA would do everything possible to get its personnel out of Iran prior to any Israeli attack but it must be careful in how it does it, Hibbs, of Carnegie Endowment, said.
If it later emerged that Amano had been warned but chose not to pass that on to Iran, Tehran might conclude that "the IAEA was party to an invasion," he added. Any IAEA staff then still in the country "would be at severe risk".
But Israel also faces a dilemma as it would want to avoid the "international opprobrium" that would come from killing IAEA inspectors, Findlay said.
"A discreet word to the IAEA Director-General hours prior to an attack would ensure that inspectors at Iranian facilities could remove themselves to Tehran or elsewhere quickly."
Goldschmidt said he did not believe the IAEA - whose main brief is to ensure that nuclear material around the world is not diverted for military purposes - would remove inspectors from Iran unless there was a "clear signal" that it should.
But if tension escalated, the IAEA might ask its inspectors whether they were volunteers to be in Iran, as was done when they were sent to inspect the research reactor in Vinca during NATO's 1999 bombing campaign against Serbia.
In the case of Iraq almost a decade ago, IAEA inspectors were withdrawn immediately after the U.S. warning without coming to any harm, "notwithstanding the tense relationship between Saddam Hussein's government and the inspectors", Findlay said.
Heinonen said Iran was responsible for the inspectors' safety under its nuclear safeguards agreement with the IAEA, but "one cannot exclude the possibility that some individuals may express their anger and frustrations on the inspectors".
(Additional reporting by Dan Williams in Jerusalem; Editing by Mark Heinrich)