How long does America still have to stop an Iranian nuclear bomb?

OPINION:

The next few months will be the last chance to prevent a nuclear Iran. Right now, an Iranian breakout is still detectable and stoppable. Its air defenses are degraded, and its means of aggression are depleted, creating a unique but fleeting opportunity that the United States must exploit before time runs out. By year’s end, one or more of these windows will likely have slammed shut.

The fundamental question that has prompted the Biden administration to discuss potential military action is the same that must drive the incoming Trump administration: How long does America still have to stop an Iranian bomb? There is still time, but not much.

Tehran just announced its largest-ever enrichment expansion, on the heels of warnings from U.S. and Israeli intelligence that it is positioning itself to finish a nuclear weapon. Iranian officials increasingly lean in by declaring their readiness to build a bomb overnight, prompting new alarms from the U.N.’s chief atomic inspector that he cannot properly track Iran’s progress.

These steps improve Iran’s ability to achieve a nuclear weapon before anyone can detect or stop it. Growing uranium stockpiles and centrifuge fleets steadily expand its ability to enrich a full arsenal’s fissile material in mere weeks. They also simplify a covert “sneak-out” at some unknown site, as well as an underground breakout at Fordo or — perhaps as soon as 2025 — the Natanz tunnel facility being excavated too deeply for Israeli or even U.S. bunker busters.

The incoming Trump administration will have to be more clear-eyed than its predecessors, which comforted themselves that, although Iran could produce weapons-grade uranium in just days, it was still years away from knowing how to build a nuclear weapon. Already in 2023, American and Israeli defense chiefs abruptly shrunk their estimates from roughly two years to only several months for Iran to complete a bomb after deciding to do so.

But even those estimates are rosy. The Manhattan Project took only one year to design and build the first implosion-type device from scratch, and recent reports indicate Iran is already far down this path — and proceeding further. Expecting Iran, which has been working covertly on a nuclear weapon for years, to progress more slowly than the engineers who had to invent the bomb 80 years ago is strategic folly.

But while an Iranian bomb might soon be an inevitability without determined action to stop it, the conditions for preventive action have never been better.

Thanks to Israel, Iran has lost the upper hand, for the first time, in its enduring standoff with the West. Hezbollah can no longer retaliate massively for an attack on Iran’s nuclear program, and the regime’s ballistic missiles proved largely ineffectual in two all-out barrages against Israel. Recent Israeli action destroyed Iran’s capacity to make more missiles while also neutralizing air defenses from Syria to Tehran that stood between Israeli warplanes and Iran’s nuclear facilities.

Iran is already working to slam this window shut. The more its other deterrents crumble, the more advanced, resilient and opaque its nuclear program becomes. Inevitably, Iran will also try to reconstitute its devastated air defenses and missile stocks, likely with help from Russia or China.

It is also looking to buy time, offering to restart nuclear talks using the same negotiators that ran circles around their Obama and Biden administration counterparts. The regime wants to clear its current zone of vulnerability by using diplomacy to sideline sanctions and military pressure, erode U.S. ultimatums, waste precious time and continue advancing its nuclear weapons program.

The United States must resist Iran’s attempts to run out the clock and seize the brief opportunity created by Israel’s degradation of Iranian defensive and offensive capabilities. In parallel with a maximum pressure campaign, the United States, Israel and other partners must maximize the credibility of military options to stop Tehran short of the bomb. Recent discussions by Trump advisers of possible kinetic action lend credibility to Iran’s nightmare scenario: a joint U.S.-Israeli military option to reverse its remarkable nuclear progress.

Iran reliably reins in its worst behaviors when facing such threats, so the incoming president should join Israel in giving the regime an ultimatum on day one: Agree fully and immediately to verifiably dismantle its nuclear weapons program or invite its imminent and utter destruction.

If Mr. Trump chooses instead to meet Iran’s shrewd and uncompromising diplomats at the negotiating table, he must set clear and short timelines measured in months or even weeks, not years. If that time runs out, the administration needs to be prepared to act swiftly, decisively and forcefully.

Mr. Trump must reverse his predecessors’ mistakes and keep one eye on the clock, the other on the exit and his foot on the gas. Either way, he cannot afford to miss the narrow opening to prevent a nuclear Iran before it’s too late.

• Blaise Misztal is vice president for policy at the Jewish Institute for National Security of America. Jonathan Ruhe is the institute’s director of foreign policy.