Rear Adm. John Kirby, the Pentagon press secretary, said U.S. officials believe the number on Sinjar is now "in the neighborhood of 4,000," and that between 1,500 and 2,000 of those are local residents who live there and have no plans to leave.
"We believe based on our assessment of conditions on the mountain that it is much less likely that we'll need to continue to airdrop any more food and water," Kirby said. The last airdrop was Wednesday.
A U.S. assessment team that spent Wednesday on the mountaintop reported numbers far smaller and circumstances less dire than feared. Two officials said they estimated that roughly 4,500 were atop the mountain, half of which were local herders.
That makes it less likely that U.S. troops will need to conduct a major rescue effort, but it does not substantially change the big picture in Iraq, which is in crisis with a problem-plagued government and an aggressive Sunni insurgency.
The Obama administration has been airdropping food on the mountain and contemplating a military-led rescue of civilians who fled there to escape the militant group known as the Islamic State. But it had been unclear how many people might need evacuation. Some had reported them to number in the tens of thousands.
After being briefed on the assessment team's trip to Sinjar Mountain, Defense Secretary Chuck Hagel said Wednesday that it was "far less likely" now that a rescue mission would be needed.
Hagel called the assessment a bit of good news. Of the U.S. effort in Iraq, he said: "It's not over. It's not complete."
Attacks across Iraq's north and west by the Islamic State and its Sunni militant allies this summer have displaced members of the minority Christian and Yazidi religious communities and threatened neighboring Iraqi Kurds in the autonomous region.
Thousands of Yazidis on the mountain were able to leave each night over the last several days, Kirby said in a statement Wednesday.
The U.S. troops and U.S. Agency for International Development staff who conducted the assessment on Sinjar â fewer than 20 people overall â did not engage in combat operations and all returned safely to Irbil by military aircraft, he said.
"The Yazidis who remain are in better condition than previously believed and continue to have access to the food and water that we have dropped," Kirby said. "We will continue to provide humanitarian assistance as needed and will protect U.S. personnel and facilities."
The U.S. Central Command said late Wednesday that four U.S. cargo planes airdropped 108 bundles of food and water to the remaining people atop the mountain. It was the seventh U.S. delivery of food and water since the relief operation began last week.
Julie Pace reported form Edgartown, Mass. Associated Press reporter Lolita C. Baldor contributed to this story.
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