NEW YORK - A bipartisan group of former US diplomats, generals and government officials Thursday cautioned the US and Israel against launching attacks on Iran's nuclear facilities, saying such a move would derail Tehran's programme for four years at most while uniting its citizens and alienating the Muslim world.

In a report - whose signatories include Brent Scowcroft, Ret. Admiral William Fallon, former Republican senator Chuck Hagel, Retd General Anthony Zinni and former Ambassador Thomas Pickering - concludes that a unilateral Israeli attack would set back the Iranian nuclear programme by only 2 years and an American attack by 4 years.
But if the objective is “ensuring that Iran never acquires a nuclear bomb,” the US “would need to conduct a significantly expanded air and sea war over a prolonged period of time, likely several years.”
In order to achieve regime change, the report says, “the occupation of Iran would require a commitment of resources and personnel greater than what the US has expended over the past 10 years in the Iraq and Afghanistan wars combined.”
While the report notes that an attack would yield some benefits - such as damaging Iran’s nuclear and military facilities and demonstrating US seriousness in preventing Iran from obtaining nuclear weapons - costs could include Iranian counter-attacks against Israel and American interests, a breakdown of the international coalition against Iran and the “increased likelihood of Iran becoming” a nuclear armed state. A sustained conflict “would boost the price of oil and further disrupt an already fragile world economy,” “could further alienate Muslims and others worldwide,” and likely “unify the [Iranian] population behind the government than to generate resistance.” The signatories also conclude:
"Serious costs to US interests would also be felt over the longer term, we believe, with problematic consequences for global and regional stability, including economic stability. A dynamic of escalation, action, and counteraction could produce serious unintended consequences that would significantly increase all of these costs and lead, potentially, to all-out regional war."
The report’s conclusions echo assessments made by various former and current American and Israeli government and military officials.
Iran insists its nuclear programme is for peaceful purpose, not geared to produce weapons.
Indeed, US and Israeli intelligence, and the International Atomic Energy Agency, have determined that the Iranian leadership has yet to decide on whether to build nuclear weapons. The report’s summary notes that “signs of an Iranian decision to build a nuclear weapon would likely be detected, and the US would have at least a month to implement a course of action.”
 “Planners and pundits ought to consider that the riots and unrest following a Web entry about an obscure film are probably a fraction of what could happen following a strike - by the Israelis or US - on Iran,” retired Lt. Gen. Gregory Newbold, an endorser of the Iran report and a former operations chief for the Joint Chiefs of Staff, said.
 “You can’t kill intellectual power,” said retired Lt. Gen. Frank Kearney, who endorsed the report, referring to the point that military strikes will not permanently end Iran’s nuclear program.
Military effectiveness notwithstanding, the New York-based group’s report concluded that “one of the most serious but difficult to quantify costs of military action against Iran could be damage to US reputation and standing.”
 “If Iran’s nuclear programme is attacked by the US or Israel in the absence of an international mandate or a multinational coalition, support for maintaining sanctions against Iran could be substantially weakened,” the report said.
Iran may retaliate by attempting to close the Strait of Hormuz, an action that would “rattle global markets and cause a significant spike in oil prices,” according to the report.
An assault would “introduce destabilizing political and economic forces in a region already experiencing major transformations,” the report said. A US strike may provoke worldwide anger among Muslims and enhance al-Qaeda’s ability to recruit new members, it said.
The report reiterates conclusions previously outlined by US officials, including Joint Chiefs of Staff Chairman Admiral Michael Mullen, about the limited effectiveness of a military attack on Iran.
A US air strike involving Northrop Grumman Corp. stealth B-2 bombers dropping 30,000 precision-guided penetrating bombs “carried out to near perfection” could delay Iran’s programme by up to four years, according to the report.
A unilateral strike by Israel “with its more limited capabilities, could delay Iran’s ability to build a bomb by up to two years,” the report said. An Israeli airstrike “is unlikely to succeed in destroying or even seriously damaging” the deeply buried Fordo enrichment facility and the stockpile of near-weapons- grade enriched uranium there.
The “lack of a high-confidence military option against Fordo is a key reason why Israeli government officials believe they must take action to destroy Iran’s supply of low-enriched uranium and damage Iran’s ability to produce more centrifuges before Fordo becomes fully operational,” the report said.