(Adds comments by U.S. attorney general )
By Ernest Scheyder and Terray Sylvester
CANNON BALL, N.D., Dec 2 (Reuters) - U.S. military veterans were building barracks on Friday at a protest camp in North Dakota to support thousands of activists who have squared off against authorities in frigid conditions to oppose a multibillion-dollar pipeline project near a Native American reservation.
Veterans volunteering to be human shields have been arriving at the Oceti Sakowin camp near the small town of Cannon Ball, where they will work with protesters who have spent months demonstrating against plans to route the Dakota Access Pipeline beneath a lake near the Standing Rock Sioux Reservation, organizers said.
The Native Americans and protesters say the $3.8 billion pipeline threatens water resources and sacred sites.
Some of the more than 2,100 veterans who signed up on the Veterans Stand for Standing Rock group's Facebook page are at the camp, with hundreds more expected during the weekend. Tribal leaders asked the veterans, who aim to form a wall in front of police to protect the protesters, to avoid confrontation with authorities and not get arrested.
Wesley Clark Jr, a writer whose father is retired U.S. Army General Wesley Clark, met with law enforcement on Friday to tell them that potentially 3,500 veterans would join the protest and the demonstrations would be carried out peacefully, protest leaders said.
The plan is for veterans to gather in Eagle Butte, a few hours away, and then travel by bus to the main protest camp, organizers said, adding that a big procession is planned for Monday.
Protesters began setting up tents, tepees and other structures in April, and the numbers swelled in August at the main camp.
Joshua Tree, 42, from Los Angeles, who has been visiting the camp for weeks at a time since September, said he felt pulled to the protest.
"Destiny called me here," he said at the main camp. "We're committed."
"GO HOME"
The protesters' voices have also been heard by companies linked to the pipeline, including banks that protesters have targeted for their financing of the pipeline.
Wells Fargo & Co said in a Thursday letter it would meet with Standing Rock elders before Jan. 1 "to discuss their concerns related to Wells Fargo's investment" in the project.
There have been violent confrontations near the route of the pipeline with state and local law enforcement, who used tear gas, rubber bullets and water hoses on the protesters, even in freezing weather.
The number of protesters in recent weeks has topped 1,000. State officials on Monday ordered them to leave the snowy camp, which is on U.S. Army Corps of Engineers land, citing harsh weather, but on Wednesday they said they would not enforce the order.