Three years ago this week, disturbing images of women and children fleeing the Islamic State in northern Iraq shocked the world. During the siege of Mt. Sinjar, reports emerged of ISIS militants ruthlessly massacring Yazidi men and kidnapping and enslaving Yazidi women and children. Girls were separated by eye color and sold to ISIS fighters based on their preference. Thousands were trapped on the mountain, desperate for food, water and rescue.

Similarly, Iraq’s ancient Christian community was in the crosshairs as ISIS attempted to establish a caliphate. Days after the Sinjar massacre, ISIS seized Qaraqosh, Iraq’s largest Christian city with a population of 50,000. Fleeing on foot, many could not escape being killed, kidnapped, or forced to convert. Churches and other holy sites that had stood for centuries were bombed, defaced or destroyed, or turned into torture chambers and weapons storehouses. The full measure of human suffering exacted against these innocent people remains incalculable.

This bloodthirsty campaign targeting ethnic and religious minorities was clearly genocide—a term I do not use lightly. At the time, I and many others urged the Obama Administration to officially recognize the Islamic State’s atrocities for what they were, and then-Secretary of State John Kerry finally did, on March 17, 2016. His declaration that ISIS is “responsible for genocide” against Christians, Yezidis and other religious minorities was only the second time in history that a U.S. secretary of state made a genocide determination—the first being Darfur. Both the U.S. Senate and House of Representatives unanimously passed resolutions denouncing this genocide.

Unfortunately, it is unclear whether the current administration maintains this determination. It is important for Secretary Tillerson to publicly address this issue and clarify the administration’s stance, which my colleagues and I have asked him to do. Even then, words without action will not change the reality on the ground. The Trump Administration must take decisive steps to counter the gravity of the situation: ISIS is seeking to erase thousands of years of history and the people who represent it.

The Bible’s Old Testament is full of references to the ancient cities and towns that comprise modern-day Iraq. Abraham hailed from Ur in southern Iraq. Isaac’s wife Rebekah was from northwest Iraq. The twelve sons of Jacob were all born in Iraq, and the spiritual revival depicted in the book of Jonah occurred in the city of Nineveh, now known as Mosul. Many of the Christians there still speak Aramaic, the language of Jesus, and trace their faith back to the Apostle Thomas. Sadly, their population in Iraq has quickly dwindled from 1.4 million a generation ago to less than 200,000 today.

If the United States fails to take meaningful steps to support these communities, including ensuring their access to humanitarian assistance and the resources they need to rebuild, even more of them will be forced to abandon their ancient homeland. This would be a tragedy on a multitude of levels, and a deathblow to the vision of a diverse, pluralistic, Iraq that respects religious freedom. The State Department has an obligation to ensure “vulnerable and persecuted religious minorities, including victims of genocide” receive humanitarian aid, as Congress directed in the most recent appropriations legislation.

I will continue to press for oversight and accountability in this area, but the Executive Branch must prioritize the issue, rather than allow the inertia of the State Department bureaucracy to dictate the path forward. President Trump should quickly end the exclusion of genocide-targeted minorities from U.S. humanitarian and reconstruction aid. A presidential directive would provide much-needed guidance to State Department and USAID personnel. I have no doubt that once Governor Sam Brownback is confirmed as ambassador-at-large for international religious freedom, he will be a stalwart advocate on behalf of these beleaguered religious communities.

Additionally, Secretary Tillerson should move swiftly to appoint a special coordinator based in northern Iraq who can directly oversee U.S. assistance and collaborate closely with local partners and civil society groups. The U.S. should not cede this important work to the United Nations Development Fund. Combining these efforts with diplomatic engagement with Iraq’s central government and the Kurdistan Regional Government, we can help guarantee the political and economic rights of these beleaguered communities, as well their return and protection.

President Obama’s misguided foreign policy did real damage to Iraq’s minorities, but these ancient communities could disappear completely on President Trump’s watch if his administration fails to help them.

Marco Rubio has been serving as U.S. Senator from Florida since 2011.