Fully destroying its nuclear program is likely to be difficult and costly.

Iran wants nuclear weapons. This rational desire aims to ensure that it can pursue its interests without fearing foreign military intervention. The United States and Israel both have rational reasons for wanting Iran never to obtain nuclear weapons. Despite its vastly inferior resources, Iran is advantaged in pursuing its goals because it simply needs to stay the course, gradually enriching nuclear material, while the United States, Israel and other involved parties must overcome significant differences that prevent a united front capable of deterring or disrupting Iran’s nuclear-weapons program. By reducing deterrence, these differences harm the diplomatic effort, making a peaceful end to Iran’s nuclear ambitions less likely.

Iran’s leaders seek regional dominance not only for ideological reasons but because being more powerful makes them less vulnerable. They saw the fate of Saddam Hussein and Moammar Gaddafi, both of whom suffered humiliating and violent deaths at the hands of a U.S.-led coalition after giving up their nuclear programs. Conversely, Pakistan and North Korea both succeeded in getting nuclear weapons despite U.S. protestations, threats and diplomacy. They raced their way to nuclear weapons and their leaders remain in power. Obtaining nuclear weapons would be a major win for Iran’s leaders. Therefore, dissuading them will be difficult, even with a united opposition.

The U.S., Israel, Western powers, Russia, China and Iran’s regional adversaries all have an interest in stopping Iran from getting nuclear weapons. But their interests are not nearly the same in terms of urgency or severity.

For Israel, a nuclear-armed Iran is an existential threat. For the countries in the region, the threat is nearly as potent. Although Iran has not promised to wipe them off the map in a nuclear holocaust, post-revolution Iran has a long history of bloody warfare, military intervention and terrorism in the Middle East. Just this week Iranian-backed Houthis launched armed drones into Saudi Arabia.

For America, a nuclear-armed Iran threatens some of its interests but not its survival. These threats include increased instability in a decreasingly important region, increased terrorism, threats to deployed military assets and threats to European allies.

The European powers appear ambivalent to the threat of Iranian nuclear weapons that would likely be able to strike their soil. They are happy to see economic sanctions removed, as well as to resume trading with Iran and purchasing its oil. Finally, Russia and China would love to see the U.S. fail to achieve a much-heralded foreign-policy objective.

There are three main approaches to thwarting Iran’s nuclear ambitions: 1) deterrence; 2) military action; and 3) diplomacy. The paths complement each other. Military action makes deterrent threats more credible, and diplomacy can make denuclearization more palatable. Coercive diplomacy is nothing new. Negotiating with someone while holding a gun to their head is still negotiating; it is just more likely to succeed.

Fully destroying Iran’s nuclear program is likely to be difficult and costly. Successful diplomacy requires deterrence because Iran’s strong preference is to get nuclear weapons. Deterrence has two components. The opponent must perceive a country or coalition as having both the necessary capabilities and resolve; neither is sufficient on its own. The fundamental problem to deterring Iran is the absence of a unified entity with both. The United States has the capabilities, and Israel and regional countries have the resolve. However, these players are currently incapable of conveying a unified purpose.

Iran sees Israel as having abundant resolve but limited capabilities and potency, while Iran has a deterrent of its own. Israel would face difficulties refueling and penetrating Iran’s deep fortifications, and whether its attack succeeds or fails, it will likely face Hezbollah and perhaps also Hamas in a multi-front war. That could result in massive damage, casualties and unabating rocket fire targeting the entire country, hitting sensitive sites and overwhelming its Iron Dome missile-defense system.

Washington has warned Israel over military action as it negotiates with Iran. An Israeli strike could ruin its relationship with its most important partner. The United States might refuse to replenish Iron Dome. Israel failed to significantly reduce the rate of fire from Gaza in its most recent altercation with Hamas last May. Israel expects thousands of rockets a day in a war with Hezbollah—many times more than Gazan terrorists were able to launch.

As is always the case with preemptive action, it’s difficult to justify casualties today to prevent potentially greater casualties in the future. However, Israel has shown on several occasions that it is willing to strike to prevent a future catastrophe, even against strong U.S. opposition.

Finally, if Iran thinks that its nuclear program can survive an Israeli strike, then it is unlikely to be deterred. Iran also sees regional powers like the Saudis who can barely contend with the Houthis, as lacking the capability to threaten Iran’s nuclear program.

Conversely, the United States has the capabilities portion of the equation but perhaps not the resolve. America and Israel have discussed military options should all other initiatives fail. However, the Biden administration has shown reluctance to risk military confrontation in the Middle East, and its disorganized and rushed exit from Afghanistan does not lend credibility to threats against Iran.

In all, there are three ways to complete the deterrence equation. The first is to boost Israel’s capabilities. Some congressmen and analysts have suggested giving Israel refueling planes and “bunker-buster” bombs. The second is to boost perceived U.S. resolve by moving military assets to the region and making public threats should Iran pass a specified red line. The best way is to marry U.S. capabilities with Israel’s resolve through joint statements and war games—the more official and public, the more credible. This is the best shot to boost deterrence and enhance diplomacy. However, unless America and Israel can close the policy gap, this is unlikely to succeed, and Iran could stall its way to a bomb.

Jeremiah Rozman is a publishing adjunct at The MirYam Institute. From 2006-2009, he served as an infantryman in the Israel Defense Forces. He is currently a second lieutenant in the U.S. Army.