An updated report from the United Nations’ nuclear watchdog, the International Atomic Energy Agency, charges that Iran has been, and probably still is, hiding a nuclear weapons program behind its nuclear energy research. This is not particularly surprising, but it is hardly good news. Despite Iran’s many denials, it seems clear that it has been seeking to establish a miniature version of mutually assured destruction in a strategic balance with Israel, an undeclared nuclear power.

The I.A.E.A. report has put additional pressure on the Security Council members Russia and China to support more aggressive economic and political sanctions against the regime in Tehran. It has provoked a new round of F-16 rattling in Israel as a parade of strategic leaks provides details about preparation for a pre-emptive military strike to neutralize the Iranian threat. Some voices in Washington have likewise called for more serious consideration of a military option.

Regarding the use of force against Iran, President Obama said, “We are not taking any options off the table.” But, diplomatic posturing aside, a military strike is just the kind of option that the United States should take off the table. A pre-emptive attack, whether conducted by the United States, Israel, the United Kingdom or all three, fails to fulfill basic just war criteria. Not only is the practical threat from Iran too difficult to assess (just cause) but the outcome of such a strike is too difficult to predict (probability of success). Any attack, moreover, could be enough to begin a widespread war in the Middle East. Iran is not Gaza. It has a conventional military capability, including medium-range missiles, that could lead to a prolonged and brutal conflict. Any attack is also likely to draw in Iran’s surrogates, Hezbollah in Lebanon and Hamas in Gaza.

Worse, such an attack is unlikely to achieve greater security for Israel. The Iranian program has been widely dispersed and driven underground. It is unlikely that an attack would succeed in crippling Iran’s nuclear weapons development; it might even accelerate the program.

But beyond the moral and strategic problems associated with a pre-emptive attack, the last thing the United States needs is to undertake another military adventure in the Islamic world. Another debt-financed war could be the final blow to the staggering U.S. economy. Investments in human capital and infrastructure, not more war-making, are where the nation’s diminished resources are most needed now.

Israel, as a sovereign power, can of course come to a different conclusion about the threat posed by Iran. Cynical observers are already suggesting that a messy conflict with the puzzling Islamic republic is just the diversion Israel needs to slow down the accelerating movement for Palestinian statehood for at least another half-decade. That would be a cruel and short-sighted calculus for Israelis and a plain disaster for Palestinians; it would also be a strategic and economic catastrophe for the rest of the world.

The global economy twitches in anxiety each market day. It remains unclear if the Arab Spring will lead to reform or ruin. As a new generation of Muslim youth begins to perceive an alternative to the violence proposed by Islamic extremism, the West could not make a more counterproductive gesture than an unprovoked attack on Iran. The Islamic Republic of Iran has already done much to diminish its legitimacy in the eyes of its own restive people; a pre-emptive strike would be just the kind of event the regime could use to reassert its hold on power.

Four rounds of U.N. sanctions have already proved somewhat effective. Peaceful options to a resolution of this stand-off remain. Previously proposed nuclear fuel swaps could provide confidence-building diplomatic successes while normalizing broader international oversight of Iranian enrichment efforts. But an attack on Iran would no doubt begin a regional war and demolish whatever prospects remain for a democratic transition in Tehran. The Obama administration needs to wave Israel off from an air strike in the clearest possible terms, publicly and privately. The penalties for such a foolish act, in terms of loss of diplomatic support and military aid, should be plainly delineated. If a bold strike is required, let it be for peace, not war. Now would be a good time for all parties to sit down for a serious discussion about what it would take to establish a nuclear-free Middle East.

An attack on Iran now would at best only further isolate Israel and drag the United States right along with it. At its worst, however, it could mark the beginning of a broader regional conflict that could have incalculable human costs, intensifying global jihad against Israel, the United States and Jews and Americans anywhere. The prospects for peace, not only in the Middle East but everywhere, would be set back for generations.