Tufts-Fletcher-News:

IRAN'S NUCLEAR PROGRAM has displaced Iraq as America's most serious foreign-policy problem. The question is whether we can live with nuclear weapons controlled by Iran's President Mahmoud Ahmadinejad and the mullahs.

President Ahmadinejad said that Iran would not be deprived of its "inalienable right" to develop nuclear power, and does not seek nuclear weapons. Despite these assurances, the ominous conclusion is that Tehran is arguably producing fissile material for nuclear weapons and defying the United Nations Security Council, as recent events suggest:

On Aug. 22, Iran refused to allow inspectors from the United Nations' nuclear watchdog group, the International Atomic Energy Agency, to visit its underground uranium-enrichment site, at Natanz.

On Aug. 28, Iran opened a new heavy-water plant for producing what many U.S., British, French and German policymakers believe is fissile material for nuclear weapons.

On Aug. 31, the Security Council deadline for Iran to freeze its enrichment program ran out, thus raising the prospect of political or economic sanctions against Iran.

What should the U.S. public and leaders conclude from these events?

Iranian nuclear weapons pose a catastrophic threat to the United States and its allies.

In classic defense terms, we do not worry about an attack by Iran, because it does not possess long-range ballistic missiles and will not for years. Further, a direct attack against the United States would lead to Iran's destruction.

The United States is secure unless Iran uses nuclear weapons in a terrorist sense. Our greatest unknown is whether Iran would provide a nuclear weapon to terrorist organizations.

Most policymakers agree that that is unlikely, but that's not the same as a guarantee to the millions of Americans or Europeans who would die.

Worse, Iran's strategic intentions are alarming.

Iran actively supports terrorist groups and movements that are committed to an Islamic jihad against the West. It provides sanctuary to al-Qaida operatives. It supports insurgents in Iraq who are killing hundreds of American soldiers and Iraqi civilians each week. It armed Hezbollah with the rockets that killed Israeli citizens in their homes in the "war" during July and August. And Iran's President Ahmadinejad said that Israel should be "wiped off the map."

The second thing Americans should conclude from the recent events is that diplomacy is vastly preferable to military intervention.

The Bush administration's policy for the last year has focused on diplomacy. Washington has built a loose coalition of France, Germany, Britain, Russia and China to persuade Iran to abandon its nuclear program.

Diplomacy is an important option because nuclear proliferation in the hands of reckless states poses a strategic threat to all states. If Iran can develop nuclear weapons without a serious diplomatic response by the international community, the credibility of the United Nations will be further weakened.

However, the risk with diplomacy is that it may mask an unsettling reality. What if Iran and other states, such as North Korea, conclude that diplomacy is a cover for states that do not have the will to confront states that threaten peace? Despite intense diplomacy, North Korea possesses nuclear weapons, and has twice tested ballistic missiles that could someday reach American cities. Will diplomacy allow Iran to develop similar capabilities?

Third to be concluded from the recent events: Prudence dictates that military intervention is always the option of last resort.

News reports suggest that Iran's nuclear program consists of several dozen facilities. Many of these are buried deep underground, to protect them against military attack.

Most analyses of military options against Iran's nuclear complex focus on air strikes, rather than an invasion. But would air strikes destroy Iran's nuclear program?

Unfortunately, the answer is no. They would, however, dramatically slow Tehran's efforts to develop nuclear weapons -- perhaps until democratic forces replaced Iran's radical theocracy.

Unquestionably, military intervention complicates matters. Iran could cut oil production and thus drive oil prices dramatically upward -- $100 a barrel and gasoline at $5 to $6 per gallon. It could unleash suicide bombers against the United States and Europe. Most worrisome, Iran could declare an Islamic jihad against the West.

Fourth to be concluded from the recent events: The choice lies somewhere between living with Iran's nuclear weapons and intervening militarily -- risking a global war between radical Islam and the West.

The conclusions for U.S. policymakers are not reassuring: 1) diplomacy alone will not dissuade Iran from developing nuclear weapons and 2) military intervention could inflame matters in the Mideast.

Iran's President Admadinejad may already see an Islamic jihad between Islam and the West that focuses on freedom versus tyranny. His May 8 letter to President Bush warned that "liberalism and democracyhave failed."

What principles should guide how the United States deals with Iran's nuclear program?

First, we cannot ignore this problem. If Iran is not a responsible steward of nuclear weapons, millions of innocent people could die.

Second, we must pursue diplomacy aggressively, despite signs of failure. While Russia and China declared that Iran's actions are not an "urgent" problem, and are unwilling to support "severe" sanctions, U.S. pressure might alter their strategy.

Third, since the risks of a nuclear-armed Iran are unacceptable and diplomacy is not succeeding, military intervention -- unilateral, if necessary -- remains a realistic option for the United States. But with considerable opposition to U.S. "unilateralism," Washington needs the support of its allies.

Fourth, unless diplomacy works, over time military intervention will emerge as the "best" option. That is a shame, because Russia and China could convince Iran of the international community's resolve. But their strategy of reining in American power is leading them to squander the opportunity to resolve this matter diplomatically.

Fifth, war against Iran is unlikely right now, but we are moving inexorably in that direction -- unless the United States decides that it can live with a nuclear-armed Iran. I would bet that the American people and their leaders would never draw that conclusion -- or they would live to regret it.

William C. Martel, an occasional contributor, is an associate professor of international security at Tufts University's Fletcher School of Law and Diplomacy.