The U.S. military said it dropped some 3,804 gallons of fresh drinking water and 16,128 ready-to-eat meals to tens of thousands of Yazidis, who are being targeted by militants in the Islamic State, formerly the Islamic State of Iraq and Syria.
Marizio Babille of UNICEF told CNN between 100 and 150 people per day were being airlifted by Iraqi security forces off the mountain.
"We are running out of time for thousands who can obviously not be reached by these airdrops," he said.
UNICEF estimates some 40,000 people are in hiding on the mountain, dozens of whom have died of extreme temperatures, and lack of food and water.
Britain and France have committed to assisting the United States in humanitarian airdrops.