The latest idea de jour on how the next U.S. administration should deal with Iran, trumpeted especially by the Hillary Clinton camp, is the need to be tougher and more aggressive in confronting Tehran. Only a stiff spine in standing up to the mullahcracy, as the argument goes, will block its expansionist desires and prevent a rising Iran from dominating the region.

This muscle-flexing approach, if done in a knee-jerk manner, is unwise and unnecessary, exaggerating both Iranian power and inflating the United States’ capacity to stop it. Instead, Washington should focus on containing Iran where it threatens vital U.S. interests and cooperating with Tehran where it serves those interests.

That said, it would be a mistake to carry a torch for the Islamic Republic. It’s a cruel and nasty regime—a serial human rights abuser at home and a promoter of policies in the region that are clearly at odds with many U.S. interests and those of its partners and allies. And it would be foolhardy to conclude that the nuclear agreement with Iran will be the last that the world sees of its flirtation with nuclear weapons. 

But creating a new Middle East bogeyman and scaring ourselves into a policy that mandates a more confrontational posture, particularly without the means and will to carry it out, makes little sense. Donald Trump has threatened to abrogate or renegotiate the Iranian nuclear agreement. Clinton has defended the accord, but her advisers seem bent on checking Iranian power in the region without outlining how they will do this or what the consequences might be.

In dealing with Iran, only two things matter: confronting and containing Iran when it challenges U.S. core interests and looking to cooperate with Tehran where it benefits those interests.

Given the near universal unhappiness in Congress with the Iranian nuclear agreement and worries that the current administration of President Barack Obama has been far too risk-averse and acquiescent in the face of Iranian expansion, a mindless default position has emerged: getting tough with Tehran without thinking through the consequences of such a policy and whether it can achieve its objectives without compromising other important U.S. interests and priorities. Lost in all of this is the politically inconvenient fact that the Iranian regime—along with Israel and perhaps Turkey—is one of the three most functional non-Arab polities in a region torn by conflict and instability, and is a rising power that isn’t so easy to push around or ignore. 

Limits to Rollback

This reality is painfully obvious when surveying the limited options available to roll back Iran’s influence in a region where Tehran has superior geographic, demographic, and political advantages. In Yemen, Iran has exploited what is essentially a very localized power struggle between the rebel Houthi forces, which it supports, and the internationally recognized government. With a low-cost investment in the Yemeni group, Iran has maximized its returns by extending its reach into Saudi Arabia’s backyard. Iran’s advantage has been further secured by an errant and ineffective Saudi bombing campaign in Yemen that has claimed thousands of civilian lives, further bolstering the Houthis’ determination. Exactly what Washington might do to contain Iran in Yemen is highly questionable. Washington’s support for the Saudi air campaign has already blackened the United States’ image. And backing one Yemeni faction against the Houthis seems like a sure way to tarnish it further without having much of an impact on the ground. The U.S. Navy has been intercepting vessels that had been smuggling arms to Yemen. But directly confronting Iran in Yemen, as some have proposed, by boarding and seizing Iranian naval vessels carrying weapons to Yemen (a country that already bears the distinction of having the most weapons per capita in the world) hardly seems prudent or effective.

In Syria and Iraq, Washington squares off against an Iran that has more assets, influence, and will to protect its interests. These arenas are vital for Tehran—to support Alawite and Shiite regimes, to ensure that there is no Sunni encirclement, and to maintain a window into Lebanon and the region. These concerns are not vital to the United States, and Washington lacks the will, skill, and staying power to treat them as if they were. To make matters worse, Iran’s interests align far more closely with Russia’s than they do with the United States’. Under these circumstances, trying to roll back Iran’s influence in Iraq or Syria directly or through a proxy war is a fool’s errand. And as long as Washington continues to believe that the nuclear agreement with Iran is in its interests, it will be reluctant and constrained to take on such a war. 

Limits to Iranian Power

As the calls for Washington to roll back Iran’s gains crescendo, any new administration must respond by basing its policy prescription on a correct diagnosis of the problem. Iran is a major power in the region and its influence will be difficult to contain, let alone roll back at a price that Washington and the American public are prepared to pay. Iran has had major sway in Lebanon, Syria, and Iraq for years and its recent adventurism in Yemen, although troubling to the Saudis, is more of a nuisance than a major strategic threat to U.S. interests. 

The notion that Iran, regardless of its assets, can establish its hegemony over a region that is predominantly Arab and Sunni Muslim and hostile toward it requires a leap of the imagination—or else, extreme paranoia. Although sectarian, ethnic, and tribal conflicts are grabbing the headlines, nobody should underestimate the continued power of Arab nationalism—a phenomenon we are seeing even in Iraq where the expansion of Iran’s influence over Shiite militias and the government is starting to encounter serious blowback from Shiite leaders within and outside the Iraqi government.

Much of the hyperbolic rhetoric about Iran that we hear in the United States obscures the reality that Tehran’s reach for regional hegemony exceeds its grasp. Its conventional military capabilities have hollowed out over the years due to neglect, sanctions, and resource constraints; it poses no credible threat of land invasion against any member state of the Gulf Cooperation Council. Sanctions relief, which is only partial to date, will free up assets for increased defense spending, but Iran has massive civilian needs that will suck up most of these dollars. However, a lack of resources has never constrained Iran’s destabilizing activities in the region. It could close the Strait of Hormuz, a vital global waterway for oil exports, for a short period of time. But unless its survival is threatened, it has no incentive to shut off its own oil commerce.

The Iranians also have strong asymmetric capabilities that they have not hesitated to use. But there may be a limit to how far Tehran will go because Iran, too, has infrastructure and critical facilities, offshore and onshore, that are vulnerable to missile, cyber, and drone attacks. Iran’s support for the murderous policies of the Bashar al-Assad regime has undermined its credibility among Sunni Arabs. Although Tehran enjoys tremendous influence among key Shiite constituencies in Iraq, it is stuck supporting two regimes in Syria and Iraq that have an extremely tenuous hold on their respective countries and face years of continued conflict, instability, and massive reconstruction costs. 

Nor have Iran’s neighbors been shy about pushing back against Iranian activities they regard as destabilizing. Tehran has been successful in plucking most of the low hanging fruit in the region, such as supporting the Houthis and enlarging its influence among Iraq’s Shiites in response to its fears over the rise of the Islamic State (also known as ISIS). But it has now assumed a key role in two countries—Syria and Iraq—that will be mired in conflict for years. It is possible that Iran’s influence in the region has hit its high watermark. To paraphrase the journalist H. L. Mencken, nobody ever went broke underestimating Iran’s ability to be its own worst enemy—to overreach and to suffer self-inflicted wounds—all of which will have a self-limiting effect on its influence.

Contain Where Necessary, Cooperate Where Possible

The next administration needs to adopt a measured and prudent strategy for containing Iran that reflects a sound understanding of the Iranian challenge, a better grasp of what could go wrong, and a clearer sense of the price that the United States is willing to pay to achieve realistic objectives. Iran is not ten feet tall. A wise and realistic policy would refrain from anti-Iranian adventures in the region when Tehran is not challenging core U.S. interests; and it would cooperate with Tehran over mutual interests, such as countering Sunni jihadi terror, stabilizing Iraq, and maintaining the Iranian nuclear accord so long as Tehran stays in compliance. A judicious policy would also avoid getting sucked further into the muck of messy regional conflicts either by directly sending in U.S. forces or by proxy. And it would certainly steer clear of actively supporting the agendas of its allies (such as Saudi Arabia in Yemen) if it damages U.S. interests. 

But an effective approach to Iran also requires containing it when its ambitions for regional hegemony present a threat to vital U.S. interests. Above all, that means defending allies and partners when their territorial integrity and independence are threatened by Iranian military attack, using force to prevent Iranian efforts to impede the flow of maritime traffic in the Persian Gulf, preventing and responding to Iranian or Iranian-sponsored terrorist attacks against U.S. facilities and military and civilian personnel, and using force to prevent Tehran from breaking out of the nuclear agreement in violation of its commitments. Maintaining a tough sanctions regime will be an indispensable tool in supplementing a credible policy of containment.

The United States can no longer afford to either hype or trivialize the Iranian threat. Washington can neither wish Iran away nor adopt a series of ill-conceived policies that attempt to weaken it, particularly in a region where Tehran has greater advantages. Washington must remain clear-eyed about its core interests. And in dealing with Iran, only two things matter: confronting and containing Iran when it challenges U.S. core interests and looking to cooperate with Tehran where it benefits those interests.

The opinions expressed here are solely those of the authors.

This article was originally published in Foreign Affairs.