Critics of a deal on Iran’s nuclear program, both in the U.S Congress and the Israeli government, need to answer a question: Is there a better alternative?

Even before we know all the details of the agreement hammered out in Geneva this weekend, there’s reason to worry about an interim accord that eases a few of the painful economic sanctions imposed on Iran in return for Iran’s freezing its drive to develop nuclear weapons. The Iranian regime has been untrustworthy for decades, and the desire for a nuclear bomb is a source of national pride and a security interest.

Yet there is a much different tone since the election of President Hassan Rouhani: The International Atomic Energy Agency reports that Iran has slowed its efforts to convert nuclear power to a bomb. This is progress; it also alters the options, notes Robert Einhorn, a former top State Department policy maker on Iran and nonproliferation.

Einhorn, now at the Brookings Institution, laid this out in a speech to an Israeli research organization last month. A perfect deal, as desired by the Israelis, isn’t attainable, Einhorn said, in evaluating any interim pact; “the better test is how it compares to alternative means.”

There are three: Retain or toughen sanctions; actively work to change the regime; or use militarily force, war. The economic sanctions have brought Iran to the negotiating table. Its oil revenue over the next six months will be $25 billion less than three years earlier, and trade and financial transactions have been curtailed.

There is considerable support in Congress for toughening the sanctions, pressuring Iran for more concessions, but there is little support elsewhere, Einhorn said. If Congress acted unilaterally, the result could be an acceleration of Iran’s nuclear program and more power for the hard-liners, he added.

“Don’t think for a moment that toughening the sanctions would cause the collapse of the ayatollahs’ regime,” said Les Gelb, a former U.S. diplomat and prolific writer about foreign policy.

Regime change sounds good, and rarely works. It did succeed 60 years ago when the U.S. toppled the regime in Iran, putting in power a corrupt dictator whose brutal rule paved the way for the anti-American ayatollahs a quarter-century later.

Undertaking military strikes against Iran’s nuclear sites is the real goal of most hawks. The Israelis have threatened this option and bitterly oppose any interim agreement. But it’s unlikely that Israel would act unilaterally, preferring action by the U.S. and its greater military capabilities.

A strike, Einhorn noted, has multiple downsides: It probably would mean the end of international sanctions, the eviction of IAEA inspectors and retaliatory terrorist actions by Iran and its surrogates.

Moreover, this would be a much bigger, and dicier, operation than, say, taking out Syria’s chemical weapons. It would require subsequent actions, and the danger of more widespread conflict is genuine. This wouldn’t sit well with the war-weary U.S. public. A Washington Post-ABC News poll last week showed voters, by a 2-to-1 margin, supported a nuclear deal with Iran.

To be sure, there are huge risks. A short-term agreement might be the high watermark of Iranian cooperation. The Israelis, Einhorn said, fear it would generate a “burst of irrational enthusiasm,” and bring pressure from global business interests to end most sanctions. The rift between two longtime allies, the U.S. and Israel ― already “the most significant ever,” according to the expert Aaron David Miller ― will get worse.

Still, even if what Iran really wants is to be a screwdriver away from having a nuclear weapon, as one observer put it, inspections will be rigorous under the discussed temporary agreement. If the Iranians try to break out and quickly weaponize, there is sufficient time to act if there’s the political will.

As Einhorn said, it would be less than a perfect deal. But which alternative would be better?

By Albert R. Hunt 

Albert R. Hunt is Washington editor at Bloomberg News. The opinions expressed are his own. ― Ed.