The United States is sending cargo planes to drop pallets of humanitarian aid and supplies to stranded Iraqi citizens threatened by the militant Islamic group ISIS, U.S. officials said today.

The air drop mission has begun, officials told ABC News.

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The emergency effort is being deployed to help a group of 40,000 Yazidis, a group of ethnic Kurds, who fled villages in northern Iraq under threat from ISIS.

The Yazidis fled to the Sinjar Mountains, in a remote part of northern Iraq near the border of Syria, where they are stuck without food or water while ISIS forces are gathered at the base of the mountains.

ISIS has overtaken much of the northern part of Iraq, including the city of Mosul, over the past two months. They are simultaneously waging campaigns for territory in Syria and Lebanon in their quest to create a unified Islamic state encompassing territory from all three countries.

The Iraqi government has had little success battling ISIS.