Thousands of military personnel and hundreds of civilians would be killed if the United States launched an air strike on Iran to prevent it developing nuclear arms, a British think tank said in a report released on Monday.
The report by the independent Oxford Research Group said any bombing of Iran by U.S. forces, or by their Israeli allies, would have to be part of a surprise attack on a range of facilities including urban areas that would catch many Iranians unprotected.
"I think there is at least a 50:50 risk of some sort of real crisis, probably with military action, before the end of next year," said the report's author, Professor Paul Rogers of the University of Bradford.
"There is always the possibility that the Israelis do (it). I don't think you can rule that out," he told Reuters.
"For the Israelis, having an Iran which is getting anywhere close to a nuclear weapons capability is simply not acceptable."
An attack could eventually lead to a lengthy confrontation involving many other countries in the region, could mean the closure of the Gulf, and would probably have a "formidable" impact on oil prices, as well as spurring new attacks by Muslim radicals on Western interests, the report said.
"A U.S. military attack on Iranian nuclear infrastructure would be the start of a protracted military confrontation," the report said.
Thousands of dead
Such a confrontation would probably involve Iraq, Israel and Lebanon as well as the United States and Iran, with the possibility of Arab Gulf states being involved as well.
"Military deaths in (the) first wave of attacks against Iran would be expected to be in the thousands," it said.
"Civilian deaths would be in the many hundreds at least," it added. "If the war evolved into a wider conflict, primarily to pre-empt or counter Iranian responses, the casualties would eventually be much higher."
Western states suspect Iran of secretly aiming to build a nuclear bomb. Tehran says its nuclear facilities are intended to produce only electricity.
Washington and Jerusalem have said they would prefer to solve the dispute through diplomacy but have not ruled out military action.
The report said an attack by the United States or Israel on Iran would probably spur Tehran to work as rapidly as possible toward developing a nuclear military option.
It said U.S. forces, already tied down in Iraq, would have a limited number of military options when dealing with Iran and would have to rely almost entirely on the air force and navy.
Any attack would have a "powerful unifying effect within Iran", bolster the Tehran government, and mean any future U.S. relationship with Iran would be based on violence.
The report concluded that a military response to the crisis would be a "particularly dangerous option and should not be considered further".