Secretary of State John Kerry said Thursday that the United States has determined that the Islamic State is carrying out genocide against Christians and other religious groups in the Middle East.
It was not immediately clear whether the declaration would result in any change in U.S. policy, including the American bombing campaign against the radical Islamist group.
"In my judgment, [ISIS] is responsible for genocide against groups in areas under its control including Yazidis, Christians and Shiite Muslims," Kerry said at the State Department.
The timing of Kerry's announcement appeared prompted by Congress, which unanimously passed a genocide resolution on Monday. The measure condemned the Sunni Muslim group that has repeatedly targeted other religious and ethnic groups.
In the summer of 2014, the Islamic State captured large swaths of territory in Iraq and Syria. As part of those advances, the Islamic State overran parts of northern Iraq, where the tiny Yazidi community has lived for centuries.
Many Yazidi women were captured and have been used as sex slaves, according to the U.S. and human rights groups. The group has also carried out repeated atrocities against Christians and Shiite Muslims.
The U.S. bombing campaign, carried out along with local ground troops in Iraq and Syria, has driven back ISIS in some areas, though it remains entrenched in large parts of Iraq and Syria.
"Without our intervention, it is clear that those people would have been slaughtered," Kerry said.
The United Nations convention against genocide, adopted in 1948 in the wake of the Holocaust, defines it as "acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group."
Prior to Thursday, the Obama administration had been reluctant to use the term, even when condemning the Islamic State in the harshest terms.
This marks the sixth time the U.S. has applied the genocide designation. The last time was in 2004 when it was used to condemn the Sudanese government for its abuses in Darfur.
On Monday, the House of Representatives passed a resolution 393-0 that labeled as genocide the ISIS atrocities against Christians in Syria and Iraq.
Congress set a Thursday deadline for the State Department to formally decide whether it would accept the genocide designation. This stepped up pressure on the Obama administration, though Kerry did not give any indication of how U.S. actions against the Islamic State might change.
Greg Myre is the international editor at NPR.org. Follow him @gregmyre1.