When US President Donald Trump announced his new Iran strategy last month, I, like many of my colleagues, was pleased to hear that countering the Islamic Republic’s regional activity and support for terrorist proxies would be a core focus.In particular, I was delighted that a proposal I introduced in 2015, to designate the Islamic Revolutionary Guard Corps for terrorism sanctions through Executive Order 13224, was finally being implemented. Targeting the IRGC with comprehensive sanctions is a welcome step toward reversing years of Iran’s regional expansionism. However, there is still much to be done. Iran’s network of terror is well entrenched throughout the Middle East, and uprooting its influence will require a broad effort that targets every instrument of Tehran’s malign activity. We in Congress are eager to contribute to this effort.For nearly four decades, Iran has fostered a number of proxies across the Middle East that it can call on to spread its influence and threaten its foes. Iran’s development of proxies stems from its military inferiority.Despite its robust ballistic missile arsenal, it lacks many of the basic military capabilities of its neighbors.Due to this major weakness and its revolutionary ethos, Tehran cultivates proxies to serve its broad strategic interests. It started in the early 1980s with Hezbollah in Lebanon and is now composed of a wide tapestry of predominately Shia terrorist organizations spread throughout the region. Hezbollah’s success as an Iranian foothold in the Levant and counterbalance to Israel has become the model from which other proxies are replicated.That is why it is vital that we strike Iran’s proxies before they mature into new Hezbollahs.The recent chaos in Iraq, Syria and Yemen has presented an opportunity for Iran to mobilize and expand its legions of foreign militias, creating many more Hezbollahs that we must confront. Some of these groups emerged a decade ago by actively targeting and killing Americans attempting to rebuild Iraq. These Shia militias were especially armed by Iran to exploit US vulnerabilities, lavishly funded to carve out significant political influence in Baghdad’s nascent democracy, and often mentored by operatives from Lebanese Hezbollah.With the American withdrawal from Iraq in December 2011, they succeeded. Unrestrained by the presence of US forces, the Iranian-backed militias gained a sizable role within Iraqi politics and society which exacerbated the sectarianism that contributed to the rise of ISIS. Since the Syrian civil war erupted in 2011, Iraqi militias have contributed heavily to the IRGC’s efforts to secure Bashar Assad’s regime.Now they are seizing much of the territory liberated from ISIS in Iraq and Syria, while murdering Sunni Arabs and Kurds who resist. This has allowed them to forge an Iranian-controlled crescent that reaches from Iran to the Mediterranean and will only further destabilize the region. Despite this, the two Iraqi militias at the center of Iran’s regional efforts elude US scrutiny. These groups are Asa’ib Ahl al-Haq and Harakat Hezbollah al-Nujaba.Asa’ib Ahl al-Haq was formed in 2006, splitting from the notorious Mahdi Army.Before the US withdrew, the group conducted over 6,000 attacks on US and coalition forces as well as foreign diplomats, contractors and even members of Iraqi government.Fighters from Asa’ib Ahl al-Haq along with their IRGC mentors are believed to have conducted the deadly 2007 assault on the Karbala Provincial Headquarters where four Americans were abducted and later executed. The group’s leader, Qais al-Khazali, has reportedly pledged allegiance to Iran’s supreme leader, Ali Khamenei, and operates under the personal supervision of Qasem Soleimani, commander of Iran’s Quds Force.Nevertheless, Asa’ib Ahl al-Haq was never designated a terrorist organization while Kata’ib Hezbollah, an allied Iraqi militia with backing from Iran, was listed as a foreign terrorist organization by the State Department in 2009.Harakat Hezbollah al-Nujaba was formed in 2013 by fighters from Asa’ib Ahl al-Haq and Kata’ib Hezbollah and also receives significant support from Iran. Its leader, Akram Kaabi, was designated as a terrorist by the US in 2009 for leading attacks on Americans in Iraq and is frequently photographed commanding proxy forces in Syria or meeting with Soleimani.Harakat Hezbollah al-Nujaba has been particularly active in eastern Syria, directly threatening US forces fighting ISIS. Specifically, the group has threatened the US garrison at al-Tanf in Syria because of its position along a route Tehran would use to supply heavy weapons to its proxies on Israel’s border.Harakat Hezbollah al-Nujaba explicitly claims to be part of this enterprise – even creating a unit dedicated to “liberating” the Golan Heights from Israel.Because of Asa’ib Ahl al-Haq and Harakat Hezbollah al-Nujaba’s key role in securing territory in Iraq and Syria for Iran’s regional ambitions and its direct threat to US forces, my Democratic colleague Brad Sherman and I have introduced The Iranian Proxies Terrorist Sanctions Act of 2017 (H.R. 4238). The bill directs the president to apply terrorism sanctions to Asa’ib Ahl al-Haq and Harakat Hezbollah al-Nujaba within 90 days of its enactment. Additionally, it requires the State Department to annually publish a list of groups receiving logistical, military or financial support from the IRGC.We believe by sanctioning these groups, we are not only restricting their funding sources but naming and shaming two prominent Iraqi organizations that are acting on Tehran’s behalf.This should cause embarrassment for the Iraqi government, which has done little to restrain the lawless behavior of its officially sanctioned Popular Mobilization Forces – of which Asa’ib Ahl al-Haq and Harakat Hezbollah al-Nujaba are members.Iraq’s leadership has a choice: It can continue to benefit from the generous relationship it has with the United States and the international community that assist it to beat back ISIS and rebuild its security forces, or it can become a client state to Iran – a nation still widely seen as a regional pariah despite the nuclear agreement.The old excuses that groups such as Asa’ib Ahl al-Haq and Harakat Hezbollah al-Nujaba are needed to combat ISIS and secure Iraq no longer hold water. With its citizens increasingly being used as pawns by the IRGC, Iraq must step up and show it is a nation of laws and responsible contributor to regional stability.We must use every instrument of national power to reverse Iran’s advance across the Middle East. There is clearly more to do, and our bill would be a good next step in a larger strategy to counter Iran. Targeting Iran’s vital proxies will send a clear signal to the region that America is committed to reversing Tehran’s advance and restoring stability. And that’s just the way it is.The author is a Republican US congressman from Texas.