President Obama should not lament but sigh in relief that Iran has rejected his nuclear deal, which was ill-conceived from the start. Under the deal, which was formally offered through the United Nations, Iran was to surrender some 2,600 pounds of lightly enriched uranium (some three-quarters of its known stockpile) to Russia, and the next year get back a supply of uranium fuel sufficient to run its Tehran research reactor for three decades. The proposal did not require Iran to halt its enrichment program, despite several United Nations Security Council resolutions demanding such a moratorium.

Iran was thus to be rewarded with much-coveted reactor fuel despite violating international law. Within a year, or sooner in light of its expanding enrichment program, Iran would almost certainly have replenished and augmented its stockpile of enriched uranium, nullifying any ostensible nonproliferation benefit of the deal.

Moreover, by providing reactor fuel, the plan would have fostered proliferation in two ways. First, Iran could have continued operating its research reactor, which has helped train Iranian scientists in weapons techniques like plutonium separation. Absent the deal, Iran's reactor will likely run out of fuel within two years, and only a half-dozen countries are able to supply fresh fuel for it. This creates significant international leverage over Iran, which should be used to compel it to halt its enrichment program.

The vast surplus of higher-enriched fuel Iran was to get under the deal would have permitted some to be diverted to its bomb program. Indeed, many experts believe that the uranium in foreign-provided fuel would be easier to enrich to weapons grade because Iran's uranium contains impurities. Obama administration officials had claimed that delivering uranium in the form of fabricated fuel would prevent further enrichment for weapons, but this is false. Separating uranium from fuel elements so that it can be enriched further is a straightforward engineering task requiring at most a few weeks.

The proposal would not have averted proliferation in the short run, because that risk always was low, but instead would have fostered it in the long run — a classic example of domestic politics undermining national security.

Tehran's rejection of the deal was likewise propelled by domestic politics — including last June's fraudulent elections and longstanding fears of Western manipulation. President Mahmoud Ahmadinejad initially embraced the deal because he realized it aided Iran's bomb program. But his domestic political opponents, whom he has tried to label as foreign agents, turned the tables by accusing him of surrendering Iran's patrimony to the West.

Under such domestic pressure, Ahmadinejad reneged. But Iran still wants reactor fuel, so he threatened to enrich uranium domestically to the 20 percent level. This is a bluff, because even if Iran could further enrich its impure uranium, it lacks the capacity to fabricate that uranium into fuel elements. His real aim is to compel the international community into providing the fuel without requiring Iran to surrender most of the enriched uranium it has on hand.

Indeed, Iran's foreign minister has now proposed just that: offering to exchange a mere quarter of Iran's enriched uranium for an immediate 10-year supply of fuel for the research reactor. This would let Iran run the reactor, retain the bulk of its enriched uranium and continue to enrich more — a bargain unacceptable even to the Obama administration.

Tehran's rejection of the original proposal is revealing. It shows that Iran, for domestic political reasons, cannot make even temporary concessions on its bomb program, regardless of incentives or sanctions. Since peaceful carrots and sticks cannot work, and an invasion would be foolhardy, the United States faces a stark choice: military airstrikes against Iran's nuclear facilities or acquiescence to Iran's acquisition of nuclear weapons.

The risks of acquiescence are obvious. Iran supplies Islamist terrorist groups in violation of international embargoes. Even Ahmadinejad's domestic opponents support this weapons traffic. If Iran acquired a nuclear arsenal, the risks would simply be too great that it could become a neighborhood bully or provide terrorists with the ultimate weapon, an atomic bomb.

As for knocking out its nuclear plants, admittedly, aerial bombing might not work. Some Iranian facilities are buried too deeply to destroy from the air. There may also be sites that American intelligence is unaware of. And military action could backfire in various ways, including by undermining Iran's political opposition, accelerating the bomb program or provoking retaliation against American forces and allies in the region.

But history suggests that military strikes could work. Israel's 1981 attack on the nearly finished Osirak reactor prevented Iraq's rapid acquisition of a plutonium-based nuclear weapon and compelled it to pursue a more gradual, uranium-based bomb program. A decade later, the Persian Gulf war uncovered and enabled the destruction of that uranium initiative, which finally deterred Saddam Hussein from further pursuit of nuclear weapons.

Incentives and sanctions will not work, but airstrikes could degrade and deter Iran's bomb program at relatively little cost or risk, and therefore are worth a try. They should be precision attacks, aimed only at nuclear facilities, to remind Iran of the many other valuable sites that could be bombed if it were foolish enough to retaliate.

The final question is, who should launch the airstrikes? Israel has shown an eagerness to do so if Iran does not stop enriching uranium, and some hawks in Washington favor letting Israel do the dirty work to avoid fueling anti-Americanism in the Islamic world.

But there are three compelling reasons that the United States itself should carry out the bombings. First, the Pentagon's weapons are better than Israel's at destroying buried facilities. Second, unlike Israel's relatively small air force, the United States military can discourage Iranian retaliation by threatening to expand the bombing campaign. Finally, because the American military has global reach, airstrikes against Iran would be a strong warning to other would-be proliferators.

Negotiation to prevent nuclear proliferation is always preferable to military action. But in the face of failed diplomacy, eschewing force is tantamount to appeasement. We have reached the point where airstrikes are the only plausible option with any prospect of preventing Iran's acquisition of nuclear weapons. Postponing military action merely provides Iran a window to expand, disperse and harden its nuclear facilities against attack. The sooner the United States takes action, the better.