The Islamic Republic of Iran has consistently proven how much damage it can cause without having access to high-tech military equipment and formal arms markets. The past few months are indeed instructive. Under a slashed defense budget and outmatched in terms of regional military spending, Iran still managed to turn-up the heat without inviting kinetic reprisal.

Western powers and Saudi Arabia have concluded Iran was behind the attack on Saudi oil installations with drones and cruise missiles, used mines to damage tankers, seized ships in the Persian Gulf, shot down a U.S. drone over international waters, engaged in hostage diplomacy, escalated its nuclear program, and broadened the scope of mayhem in Iraq, Lebanon, Syria, and Yemen through its partners and proxies. Now imagine what improved Iranian military capabilities might mean for the future.

Next October, on the fifth anniversary of the Iran nuclear deal, or Joint Comprehensive Plan of Action’s (JCPOA) so-called “Adoption Day,” an international embargo on military-related transfers to and from Iran will end. Before this happens, Washington can take action to extend the UN-based arms embargo, as well as reinforce its policy of sanctioning Iranian arms transfers. The sooner, the better.

The Islamic Republic has faced U.S. sanctions, including an arms embargo, since 1984 – the year Washington put Tehran on the “state sponsors of terrorism” list. These penalties helped impede Iran’s modernization, following the bloody 1980-1988 Iran-Iraq War, of military systems that used American technology. But starting in 2006, when the International Atomic Energy Agency (IAEA) Board of Governors voted to refer Tehran’s nuclear file to the UN Security Council (UNSC), the country was increasingly subject to multilateral sanctions, and eventually, a global ban on all imports and exports of arms and military-related equipment. These penalties were scaled back in 2015 as part of UNSC Resolution 2231, which codified the nuclear deal and set the five-year timeline for a complete lifting of the arms embargo.

The decision to relieve international pressure on Iran’s military-related procurement and proliferation functioned like a sweetener in the final stages of negotiations with Tehran. Notably, the chairman of the Joint Chiefs of Staff at the time of the negotiations, Gen. Martin Dempsey, categorically opposed any concession on military and arms exports. Yet Tehran insisted, so the five-year clock started ticking.

As the military embargo approaches its expiration date, Tehran has tightened military ties with powers hostile to Washington. Several high-level bilateral visits have occurred as Iran signed military agreements with Russia and China in the years since the JCPOA entered into force. The pacts cover strategic and military matters, and Iran reportedly weighs a future $10 billion deal to import Russian “T-90 tanks, artillery systems, planes and helicopters.” Just last month, Iran proclaimed that together with China and Russia, it plans to hold joint naval exercises in international waters.

Even though Russia and China have never totally abided by UNSC mandates, to date, they do not appear to have flagrantly violated the injunction against arms sales to Iran. Soon, though, there will be no reason for abstinence. And just because there has been no formal acquisitions since the JCPOA does not mean attempts at illicit procurement have ceased by Iran.

To be clear, removing UN restraints on imports of weapons does not mean that the Islamic Republic will become a major conventional military power overnight. Rather, the regime will likely take advantage to increase the lethality of its asymmetric and hybrid military threats.

One thing Iran might do is move to narrow the quantitative and qualitative gap between its ballistic and cruise missile systems through procurement from countries like Russia and China, with advanced cruise missile and Anti-Access/Area-Denial capabilities. Doing so, coupled with improving missile and air defense systems while simultaneously modernizing and growing select platforms – such as Iran’s Russian provided Kilo-class submarines – could be sufficient to make the Islamic Republic feel stronger and safer, thus underwriting further expansion and escalation.

Washington can play a major role in forestalling enhancements of Iran’s military systems and the deepening of its partnerships by making clear that it will enact secondary sanctions against any entity, whether Russian, Chinese, or otherwise, that exports military items to Iran. The threat of U.S. sanctions has a significant effect on both state and private entities’ willingness to do business, as was recently witnessed in the case of a Chinese energy giant and the Iranian gas sector. Washington will also need to think of clever ways to prevent Iran from using funds held in escrow accounts abroad as a line of credit against such purchases, or simply bartering oil for weapons.

Iran’s arms exports are an altogether different matter. Several UNSC resolutions contain arms transfer bans that specifically refer to regional hotspots, such as Lebanon and Yemen. Iran has consistently violated the letter and spirit of those resolutions through its low-level proliferation of systems that enable its allies to grow in influence and live to fight another day.

For instance, Lebanese Hezbollah has gone from a band of Iran-backed militants in the Levant to masters of the Lebanese state, are battle-hardened from the Syrian war, and now in possession of increasingly precise munitions that threaten Israel. Iran’s arms transfers that violate resolution 2231, be it to the Houthis in Yemen or Shiite militias in Iraq, are only the latest measures of the same problem.

In addition to refusing to observe the end of the arms embargo and sanctioning those that don’t, Washington will need to work with local partners to better erect a legal architecture, and later act on through interdictions, the supply and sale of any weapons systems from Iran or territory controlled by its proxy to other actors.

More broadly, the U.S. desperately needs to work with its European allies to get a better and more comprehensive agreement in place that addresses not just the nuclear issue, but the regional security situation. France, Germany, and the United Kingdom all voiced their support for a broader deal after they concluded that Iran was behind the drone and missile attacks against Saudi Arabia. That moment of convergence in the trans-Atlantic position should be capitalized on. Washington needs to roll this sentiment into a coalition of countries that refuse to recognize the lifting of the military embargo and support a replacement.

With increased capabilities and more accurate equipment, the threat from Tehran will only grow. Washington and the international community should not sit idly by as the Islamic Republic capitalizes on an international own-goal from 2015 and prepares a shopping spree for 2020.

Behnam Ben Taleblu is a senior fellow at the Foundation for Defense of Democracies (FDD) where he focuses on Iranian security and political issues.

Andrea Stricker is a research fellow at FDD where she conducts research on nonproliferation, Iran, North Korea, and other security policy topics.