Speaking ahead of the release of the 2016 International Religious Freedom Reports, Rex W Tillerson told reporters gathered in the State Department's Treaty Room: "ISIS has and continues to target members of multiple religions and ethnicities for rape, kidnapping, enslavement, and death.
"ISIS is clearly responsible for genocide against Yezidis, Christians, and Shia Muslims in areas it controlled. ISIS is also responsible for crimes against humanity and ethnic cleansing directed at these same groups, and in some cases against Sunni Muslims, Kurds, and other minorities."
Rumours circulated last month that genocide would no longer be officially used.
In response to this, a group of senators sent a letter to Tillerson "regarding disturbing reports that the State Department's Office of the Legal Adviser has sought to undermine and perhaps roll back" his the work of his predecessor, John Kerry that stated ISIS is 'responsible for genocide' against Christians, Yezidis and other religious minorities".
State Department spokeswoman Heather Nauert later clarified that the word "has not been removed" and said Tillerson "firmly believes" the actions of ISIS constitute genocide.
The United Nations Convention on the Prevention and Punishment of the Crime of Genocide describes genocide as "a crime under international law" which signatories, including the United States, should "prevent and to punish." This has led to previous administrations being cautious about describing a conflict as genocide.
Countries are not however forced to commit to responding to genocide with any specific actions.
Tillerson added: "The protection of these groups - and others who are targets of violent extremism - remains a human rights priority for the Trump Administration."
President Donald Trump also highlighted the need for Christians and other minority groups to be protected from persecution from the terrorist organisation.
He said: "From the beginning, America has been a place that has cherished the freedom of worship. Sadly, many around the globe do not enjoy this freedom...[We] pray for the strength and wisdom to achieve a better tomorrow - one where good people of all faiths, Christians and Muslims and Jewish and Hindu, can follow their hearts and worship according to their conscience."
Christian charity ADF which advocates for the right of people to freely live out their faith said: "With the help of our supporters and partners, we won the battle over whether ISIS is responsible for genocide against Christians, as well as Yizidis and Shia, and whether it's important to state this officially before moving on!
"Secretary Tillerson answered both emphatically in the affirmative."
