(Recasts with U.S. team landing on Mount Sinjar, adds Washington dateline and additional byline)
By Arshad Mohammed and Jeff Mason
WASHINGTON/EDGARTOWN, Mass., Aug 13 (Reuters) - A team of U.S. military and humanitarian aid personnel landed on Iraq's Mount Sinjar early on Wednesday to assess how to evacuate thousands of civilians under siege from Sunni militant fighters, a U.S. official said.
The United States has not ruled out using American ground forces in an operation to extract the trapped civilians, but they will not engage in combat, the White House said.
The U.S. team flew in darkness early in the morning to Mount Sinjar, where thousands of members of the Yazidi religious minority fled to escape an advance by Islamic State fighters, the official said.
"They were there last night and they did an assessment," the official said.
A second U.S. official said fewer than 20 personnel were involved in the assessment of the situation and all had returned safely to the Kurdistan capital of Arbil by military air.
A team of 130 U.S. military personnel is in Arbil, urgently drawing up options ranging from creating a safe corridor to an airlift to rescue those besieged on Mount Sinjar for over a week, most of them members of the Yazidi religious minority.
"These 130 personnel are not going to be in a combat role in Iraq," White House deputy national security adviser Ben Rhodes told reporters traveling with President Barack Obama, who is on vacation on Martha's Vineyard island in Massachusetts.
Rhodes noted that Obama had repeatedly ruled out "reintroducing U.S. forces into combat on the ground in Iraq." But he added: "There are a variety of ways in which we can support the safe removal of those people from the mountain."
Rhodes said the intention was to work with Kurdish forces already operating in the region and with the Iraqi military.
Kurdish fighters had been guarding Yazidi towns when armed Islamic State convoys swept in, and have already helped many thousand escape to safe areas to the north.
Obama has been deeply reluctant to revive any military role in Iraq after withdrawing the last combat troops in 2011 to end eight years of costly war that eroded the United States' reputation around the world.
SAFE CORRIDOR OR AIRLIFT
The president agreed last Thursday to send back more than 700 troops to help advise and guide Iraqi and Kurdish forces after a devastating sweep across northwestern Iraq by the Sunni Islamic State radicals, who have declared a caliphate covering much of the country.
U.S. warplanes have since carried out a series of attacks on Islamic State forces, including on forces approaching Arbil, the capital of the semi-autonomous Kurdish region, and on roadblocks and artillery around Mount Sinjar to the west.
Army Colonel Steve Warren, a Pentagon spokesman, said on Wednesday that the air attacks, combined with operations by Kurdistan's Peshmerga armed forces, had "slowed, if not stopped" attacks on the terrified families who had fled to the mountain.
Rhodes said the team in Arbil would report proposals in a matter of days for rescuing those trapped without food and water on the rocky crags of the mountain, where temperatures reach over 40 degrees Celsius (100 degrees Fahrenheit).
"You look at corridors, you look at airlifts, you look at different ways to move people who are in a very dangerous place on that mountain to a safer position," he said.
"We obviously have not just U.S. personnel who could potentially be engaged in that type of effort: We have Kurdish forces who are engaged in the area. ... We have international partners who also want to support the provision of humanitarian assistance," he said.
U.S. and British military forces have been dropping supplies of food and water to those on Mount Sinjar in the last week and Rhodes said other countries were also offering to help, including Australia, Canada and France.
U.N. agencies have rushed emergency supplies to the Dohuk region by the Syrian and Turkish borders, where the office of the U.N. High Commissioner for Refugees says about 400,000 refugees have fled, including Yazidis, Christians and other minorities.
The Pentagon said the team of 130 in Arbil, assembled there on Tuesday from different places in the region, had at their disposal four V-22 Osprey tilt-rotor aircraft, which can land and take off vertically.
It was unclear whether there was consideration being given to using the Ospreys for airlifting any of the Yazidis out, but each one would only be able to carry a couple of dozen people. (Reporting by Jeff Mason in Edgartown, and David Alexander, Arshad Mohammed and Mark Felsenthal in Washington; Writing by David Storey and Eric Beech; Editing by Ken Wills)