The Nightmare This Time

According to a recent Gallup poll, most Americans now view Iran as our country's greatest national enemy. Indeed, a Washington Post-ABC News survey reports that 42 percent of Americans support a military strike to prevent Iran from developing nuclear technology. Online betting sites make the odds of a US or Israeli airstrike against Iran before March 2007 as 1 in 3.

As Senator John McCain has summed up the hard-line position, 'There is only one thing worse than the US exercising a military option, and that is a nuclear-armed Iran."

On the other hand, some commentators, even in the administration, now suggest that a nuclear-armed Iran is inevitable. 'Look, the Pakistanis and the North Koreans got the bomb," a 'senior official" told The New York Times, 'and they didn't have Iran's money or engineering expertise."

As citizens, we are watching a slow-mo Cuban missile crisis in which events are moving, seemingly inexorably, toward a crossroads at which President Bush will have to decide between McCain's options. Before we get there, however, Americans should vigorously debate the bottom-line question: Can we live with a nuclear Iran?

Barry Posen, professor of political science at MIT, has presented the most cogent argument for the proposition that 'we could readily manage a nuclear Iran." Writing recently on The New York Times op-ed page, he identified and refuted the two most commonly cited reasons for opposing a nuclear Iran: that it would attempt to destroy Israel or strike the United States. Such an action, he rightly argues, would be suicidal for the Iranian regime. In either case, a nuclear attack would trigger overwhelming retaliation that could end life in Persia for a century to come.

Yet Posen's attempt to deal with a third concern-namely, Iran's transfer of nuclear weapons to terrorists who might use them-is less satisfactory. Relying on the Cold War logic of deterrence, he asserts that 'Iran would have to worry that the victim would discover the weapon's origin and visit a terrible revenge on Iran."

Worry, yes. But Israel and the US have to worry even more about an Iranian president who denies the Holocaust and asserts that 'Israel must be wiped off the map." Might he not also believe that he could sneak a weapon to Al Qaeda, Hamas, or Hezbollah with no fingerprints?

Tehran might not be overly concerned about getting caught-and with good reason. If a terrorist exploded a nuclear bomb in Tel Aviv or Boston, Iran would not be the only suspected source. The bomb could have come from Pakistan, Russia, or elsewhere in the former Soviet Union, where thousands of potential nuclear weapons are vulnerable to theft.

The US government is actively pursuing improvements in its nuclear forensic capability to increase the likelihood that it could identify the fissile material that powered a terrorist's bomb. But it's worth noting that more than two years after Libya's Khadafy disclosed his nuclear activities, the US has yet to conclude which nation provided him with enough uranium hexafluoride to make a nuclear bomb.

Before accepting the answer that the US can deal with an Iranian nuclear bomb, four further risks must be weighed: the threat of proliferation, the danger of an accidental or unauthorized nuclear launch, the risk of theft of an Iranian weapon or materials, and the prospect of a preemptive Israeli attack.

'A cascade of proliferation'

The current nonproliferation regime is a set of agreements between the nuclear 'haves" and 'have-nots," including the Nuclear Nonproliferation Treaty, in which 184 nations agreed to eschew nuclear weapons and existing nuclear weapons states pledged to sharply diminish the role of such weapons in international politics. Since 1970, the treaty has stopped the spread of nuclear weapons with only two exceptions (India and Pakistan).

UN Secretary General Kofi Annan's High Level Panel on Threats, Challenges, and Change warned in December 2004 that current developments in Iran and North Korea threatened to erode the entire nonproliferation regime to a point of 'irreversibility" that could trigger a 'cascade of proliferation." If Iran crosses its nuclear finish line, a Middle Eastern cascade of new nuclear weapons states could produce the first multiparty nuclear arms race, far more volatile than the Cold War competition between the US and USSR.

Given Egypt's historic role as the leader of the Arab Middle East, the prospects of it living unarmed alongside a nuclear Persia are very low. The International Atomic Energy Agency's reports of clandestine nuclear experiments hint that Cairo may have considered this possibility. Were Saudi Arabia to buy a dozen nuclear warheads that could be mated to the Chinese medium-range ballistic missiles it purchased secretly in the 1980s, few in the American intelligence community would be surprised. Given its role as the major financier of Pakistan's clandestine nuclear program in the 1980s, it is not out of the question that Riyadh and Islamabad have made secret arrangements for this contingency.

In 1962, bilateral competition between the US and the Soviet Union led to the Cuban missile crisis, which historians now call 'the most dangerous moment in human history." After the crisis, President Kennedy estimated the likelihood of nuclear war as 'between 1 in 3 and even." A multiparty nuclear arms race in the Middle East would be like playing Russian roulette with five bullets in a six-chamber revolver-dramatically increasing the likelihood of a regional nuclear war.

Accidental or unauthorized nuclear launch

A new nuclear state goes through a period of 'nuclear adolescence" that poses special dangers of accidental or unauthorized use-and Iran would be no different. When a state first acquires a small number of nuclear weapons, those weapons become a tempting target: Successful attack would disarm any capacity to retaliate with nuclear weapons. Fearing preemption, new nuclear weapons states rationally adopt loose command and control arrangements. But control arrangements loose enough to guard against decapitation inherently mean more fingers on more triggers and consequently more prospects of a nuclear weapons launch.

Theft from an uncertain Iranian regime

For outsiders, Iran appears to be a black box. Beneath this exterior, however, there are multiple centers of power and competing security structures. The supreme leader, Ayatollah Ali Khamenei, who commands the armed forces, appears to have the last word on nuclear policy. But three other groups share constitutional authority over foreign policy with the leader: President Mahmoud Ahmadinejad; former president Ali Akbar Hashemi Rafsanjani as head of the Expediency Council, which resolves conflicts among government branches; and the Foreign Ministry. Sharp differences among these groups reveal themselves in contradictory statements.

Could rogue elements within Iran's nuclear or security establishment divert nuclear weapons or nuclear materials to other nations or to terrorists? Stop and think about what we have learned recently about the father of Pakistan's nuclear bomb, A.Q. Khan. Over the decade of the 1990s, he became the first global nuclear black marketer, running what Mohamed ElBaradei, the director of the International Atomic Energy Agency, has called a 'Wal-Mart of private-sector proliferation." His network sold to Libya, North Korea, Iran, and others, nuclear warhead designs, technologies for producing nuclear weapons, and even the uranium hexafluoride precursor of nuclear bomb fuel.

An Israeli attack onIran's nuclear facilities

Lieutenant General Dan Halutz, the Israeli military's chief of staff, has called an Iranian nuclear bomb 'Israel's sole existential threat." Acting Prime Minister Ehud Olmert has warned unambiguously: 'Under no circumstances, and at no point, can Israel allow anyone with these kinds of malicious designs against us to have control of weapons of destruction that can threaten our existence."

The Israeli national security establishment has focused anxiously on a red line that Iran will cross when it achieves 'technical independence"-sufficient knowledge about how to construct and operate a limited cascade of centrifuges that could produce enough highly enriched uranium for its own nuclear bombs. The head of Mossad, Israel's secret service, states publicly that Iran could cross that red line by July. In contrast, Washington talks about a different, and much later, red line: when Iran achieves industrial-level production of enriched uranium, or even operates an industrial-level production facility long enough to produce sufficient material for a bomb. Although US estimates differ, none predict this will occur sooner than five years from now. The danger, therefore, is that Israel will make up its mind to strike Iran before the US has had time to fully consider its options.

Israel will not ask for American permission before attacking Iranian nuclear facilities at Isfahan and Natanz. But the US will be blamed throughout the Middle East as a hidden coconspirator. Retaliation by the Iranian government and by those who sympathize with Osama bin Laden will target not only Israelis, but also Americans and American interests, including oil-tanker traffic in the Persian Gulf.

As Henry A. Kissinger has noted, a defining challenge for statesmen is to recognize 'a change in the international environment so likely to undermine national security that it must be resisted no matter what form the threat takes or how ostensibly legitimate it appears." Iran's emergence as a nuclear armed state would constitute just such a catastrophic transformation for the United States. But just as JFK refused to choose between accepting nuclear weapons in Cuba or attacking the Soviet Union during the Cuban missile crisis, the challenge today is to find additional options, short of war, to stop Iran's acquisition of nuclear arms.

Graham Allison, author of 'Nuclear Terrorism: The Ultimate Preventable Catastrophe" (2004), is director of the Belfer Center for Science and International Affairs at Harvard University's Kennedy School of Government