If Iran and world powers are able to revive the 2015 Joint Comprehensive Plan of Action in the coming months, they will very likely do so without making any major modifications to the original deal. But the debate is gearing up over what issues will be the subject of follow-on talks (if there will be follow-on talks at all), and Iran’s ballistic missiles frequently top the list. For example, in January, before taking up his post as the U.S. National Security Advisor, Jake Sullivan stated that Iran’s ballistic missile program “has to be on the table” as part of any follow-on negotiations.

The repeated yet vague mentions of curbing Iran’s missile program have largely concealed the fact that it comprises not one single problem, but two: Iran’s potential development of long-range missiles that could reach Western Europe and the United States on one hand, and its proliferation of rockets and missiles to proxy groups in the Middle East on the other. While accepting this framing may make the task of containing Iran’s ballistic missile program seem more daunting, it also opens up more possibilities for solutions.

The long-range missile problem

The first problem is how to slow or prevent altogether Iran’s future development of missiles that could reach Western Europe or the United States.

Iran professes to adhere to a voluntary 2,000-kilometer (km) range limit on its ballistic missiles, meaning that, for now, these cannot reach very far beyond the Middle East. The 2000-km limit has been in place at least since 2017, when then-commander of the Islamic Revolutionary Guard Corps (IRGC) Mohammad Ali Jafari told reporters Iran simply did not need missiles with longer ranges, since it could already strike all of its adversaries, including U.S. bases in the region. Iran apparently continues to abide by the restriction, with several systems that go right up to 2,000 km but none that clearly go beyond it.

However, there are indications that Iran is establishing a technological base to build missiles with ranges much greater than 2,000 km. For example, the Zoljanah space-launch vehicle, revealed on February 1, 2021, is estimated to be capable of traveling roughly 5,000 km if launched on a ballistic trajectory. Although the Zoljanah is optimized for putting a satellite into orbit and is not a missile, its engine technology could be carried over to benefit Iran’s missile program. And recent activity at Iran’s solid-fuel development site at Shahroud, first identified by open-source analyst David Schmerler, suggests the IRGC may be working on even bigger solid-fuel motors.

The good news is that it’s not too late, and the 2,000-km range cap presents a natural starting point for a diplomatic goal. Even if an agreement limiting Iran’s missiles to 2,000-km ranges cannot be achieved, Iran may be willing keep its missiles under intercontinental ranges (5,500 km), if offered the right incentives. Those incentives might include additional sanctions relief, a green light for certain conventional arms transfers that Iran might seek, or international recognition of and collaboration with Iran’s civil space program.

Of course, many experts believe Iran will never negotiate away its missile capabilities. After all, Iranians view missile force as a “crown jewel,” and many officials, going all the way up to the Supreme Leader, have insisted that they are non-negotiable. And even if it were to negotiate, Iran would drive a harder bargain on missiles than it did on its nuclear program, precisely because missiles play such a key role in the national defense. Iran may even demand that other countries in the region, notably Israel and Saudi Arabia, both of which are thought to have missiles with ranges greater than 2,000 km, abide by whatever restrictions it agrees to.

The proliferation problem

But the long-range missile problem, formidable as it is, is not the only challenge posed by Iran’s ballistic missile program.

Iran’s transfer of artillery rocket and missile technology to proxies throughout the Middle East, dating back to at least the early 2000s, constitutes a separate problem. Tehran’s strategy for proliferating these weapons has become increasingly sophisticated in recent years, complicating any would-be interdiction efforts. Today, Iran supplies rocket and missile technology to partners in Gaza, Iraq, Lebanon, Syria, and Yemen.

Iran’s supply of complete systems, disassembled for transport, is problematic enough on its own. For example, it has sent variants of its short-range, liquid-fueled Qiam missile to the Houthis in Yemen. In late 2017, the Houthis launched Qiam variants, which they dubbed the Burkan-2, against Riyadh. Subsequently, the Houthis unveiled what they called the Burkan-3 and the Zulfiqar,both of which are also variants of the Qiam, and again used them to strike targets in Saudi Arabia. Similarly, in 2014 an Iranian official confirmed that Iran had supplied its Fateh-110 missiles directly to Hezbollah.

But an even thornier aspect of Iran’s missile proliferation is its provision of guidance kits to upgrade partners’ existing weapons stocks. In the case of Hezbollah, a guidance kit can turn an unguided Zelzal rocket into a much more accurate and lethal weapon. And smuggling a few small parts—small enough to fit in suitcases—is much easier than sending entire missiles, making it exceedingly difficult for other countries to track, let alone prevent.

Iran’s provision of manufacturing capabilities to its partners is yet another aspect of the problem. It was reported in 2008 that Iran was cooperating with Syria to help it produce its own version of the Fateh-110. In Gaza, Hamas and Palestinian Islamic Jihad have been producing increasingly sophisticated rockets in recent years, undoubtedly with the help of Iran. In the same vein, in 2018, Reuters reported that in addition to sending a “couple of dozen” complete missiles to Shi’ite militia groups in Iraq, Iran was also helping them build factories to manufacture their own missiles.

Although Iran’s proliferation of missiles and missile technology is a more complex problem than the issue of its long-range missiles, Iranian officials may be more willing to negotiate on it. According to a recent RAND report, Iran’s supply of missiles to proxies is little debated among elites in Iran, meaning it may be more domestically palatable for Iranian officials to negotiate constraints. And while Iran views its support for proxy groups in general as a key pillar of its defense, this support need not include the provision of missiles.

The Missile Technology Control Regime (MTCR), the only international precedent for controlling the proliferation of missile technology, may provide a starting point for potential solutions. The MTCR is a voluntary export control agreement among 35 countries aimed at limiting the spread of delivery systems for weapons of mass destruction, with a particular focus on systems capable of delivering a payload of at least 500 kg (1,100 lb) to a range of at least 300 km (190 miles).

Although the vast majority of missile systems that it supplies to its partners fall under the 500 kg–300 km threshold, if Iran did agree to abide by MTCR-type restrictions, it could restrain the most dangerous aspects of Iran’s missile proliferation and limit qualitative improvements in its proxies’ missile forces.

To help induce Iran to accept limitations on its missile exports, the United States could again offer narrow sanctions relief for Iranian entities currently listed for supporting proliferation or terrorism. It could also work with other countries in the region to try and address the perceived threats and root causes that drive Iran’s missile proliferation.

In short, there are really two key issues related to Iran’s ballistic missiles, not one. Although there are few easy answers to either of these, a proper framing is an essential starting point to open up a broader set of ideas and potential solutions.