The International Atomic Energy Agency is set to release a report today offering further proof that the Iranian regime is bent on acquiring nuclear weapons.

No intelligence is entirely dispositive, but the evidence on hand about Iran’s nuclear activities, even before the release of the latest report, is fairly persuasive, and the IAEA isn’t known to be a den of neoconservative war-plotting. It isn’t interested in giving Israel a pretext for a preemptive attack on Iran unless it has to.

The question now is what Israel -- or the U.S. -- will do about it.

The Israeli case for preemption is compelling, and has been for some time. The leaders of Iran are eliminationist anti-Semites; men who, for reasons of theology, view the state of the Jews as a “cancer.” They have repeatedly called for Israel’s destruction and worked to hasten that end, mainly by providing material support and training to two organizations, Hamas and Hezbollah, that specialize in the slaughter of innocent Jews. Iran’s leaders are men who deny the Holocaust while promising another.

‘Apocalyptic Cult’

An Iran with nuclear weapons may be unbearable for Israel. It would further empower Israel’s terrorist enemies, who would be able to commit atrocities under the protection of an atomic umbrella. It would mean the end of the peace process, as no Arab state in the shadow of a nuclear Iran would dare make a separate peace with Israel. And it isn’t too much to imagine that some of Iran’s more mystically minded leaders, mesmerized by visions of the apocalypse, would actually consider using a nuclear weapon on Israel -- a country so small that a single detonation could cripple it permanently.

The Israeli prime minister, Benjamin Netanyahu, who once told me he believes that Iran is led by a “messianic, apocalyptic cult,” is correct to view Iran as a threat to his country’s existence.

And yet, a preemptive Israeli attack on Iran’s nuclear facilities could be a grievous mistake. For one thing, it may already be too late. The Iranians may have dispersed and hardened their nuclear program to the point that an Israeli strike would do only glancing damage. The Israeli Air Force, as good as it is, would be stretched to its limit by such an operation.

The morality of a strike, which could cause substantial Iranian casualties, would be questioned even by those sympathetic to Israel’s dilemma. Israel will have succeeded in casting Iran as a victim and itself as something of a rogue nation. The international isolation it would experience could be catastrophic in itself. A strike might also endanger Americans in the Middle East and beyond.

A bigger problem posed by an attack, from Israel’s perspective, is that it could bring intense retaliation by Iran against civilian targets. It’s not clear that Hezbollah, which maintains an enormous rocket force in Lebanon, would join an Iranian barrage of Israel, but it’s a threat that can’t be discounted. Hundreds, maybe thousands, of Israelis could die in retaliatory missile strikes and terrorist attacks. In other words, by countering a theoretical nightmare, an Iran with nuclear weapons, Israel could bring about an actual nightmare: an Iranian conventional attack.

There are other options. Sabotage by Israeli, American and British intelligence agencies has already stymied the Iranian nuclear program, and these efforts could conceivably be accelerated and intensified. That’s certainly the view of intelligence officials I’ve spoken to in Washington and Israel.

Obama’s Choices

Which brings us to the single most important player in this drama: President Barack Obama. He has said, repeatedly, that an Iran with nuclear weapons is unacceptable to the U.S. Many Israelis, and many Americans, think Obama is soft on such matters. But I believe, based on interviews inside and outside the White House, that he would consider using force -- missile strikes, mainly -- to stop the Iranians from crossing the nuclear threshold. Why? Four reasons:

First, Iran and the U.S. have been waging a three-decade war for domination of the Middle East. If Iran goes nuclear, it will have won this war. American power in the Middle East will have been eclipsed, and Obama will look toothless.

Second, every U.S. ally in the Middle East -- Israel, the Gulf countries and Turkey, especially -- fears a nuclear Iran. The president would have their complete support.

Third, the president is ideologically committed to a world without nuclear weapons. If Iran gets the bomb, it will set off an arms race in the world’s most volatile region. At the very least, Saudi Arabia and Turkey will seek nuclear weapons. It would mark a bitter defeat for Obama to have inadvertently overseen the greatest expansion of the nuclear arms club in recent history.

Finally, the president has a deep understanding of Jewish history, and is repulsed by Iranian anti-Semitism. He doesn’t want to be remembered as the president who failed to guarantee Israel’s existence.

This isn’t to say that Obama has decided to use whatever means necessary to stop Iran. (He faces opposition in the Pentagon, for one thing, though the U.S. military has much greater capabilities than Israel.) Nor is a U.S. strike something desirable, even if done in concert with Western allies. It’s far better for the Iranians to be persuaded through other means to stop their nuclear program.

But numerous Israeli officials have told me that they are much less likely to recommend a preemptive strike of their own if they were reasonably sure that Obama was willing to use force. And if Iran’s leaders feared there was a real chance of a U.S. attack, they might actually modify their behavior. I believe Obama would use force -- and that he should make that perfectly clear to the Iranians.

(Jeffrey Goldberg is a Bloomberg View columnist and a national correspondent for the Atlantic. The opinions expressed are his own.)

To contact the author of this column: Jeffrey Goldberg at goldberg.atlantic@gmail.com.

To contact the editor responsible for this column: Timothy Lavin at tlavin1@bloomberg.net.