CANNON BALL, N.D. – Cheers, prayer and song rang out as word spread among protesters here who for months have blocked a final link of a giant oil pipeline: The U.S. Army Corps of Engineers had put up a barrier of its own.

"The Department of the Army will not approve an easement that would allow the proposed Dakota Access Pipeline to cross under Lake Oahe in North Dakota," Jo-Ellen Darcy, the Army's Assistant Secretary for Civil Works, said in a statement on Sunday.

Darcy said she based her decision on "a need to explore alternate routes for the Dakota Access Pipeline crossing." Her office announced on Nov. 14 that it was delaying the decision on the easement to allow for discussions with the Standing Rock Sioux tribe, whose reservation lies a half-mile south of the proposed crossing. Tribal officials have expressed repeated concerns over the risk that a pipeline rupture or spill could pose to its water supply and treaty rights.

North Dakota Gov. Jack Dalrymple called the Corps' decision "a serious mistake" in a statement, saying it "prolongs the serious problems" that law enforcement faces and "prolongs the dangerous situation" of people camping in cold, snowy conditions.

"We know the fight's not over just yet, but we aren't giving up," an organizer announced to a happy throng around a fire in the center of a camp where thousands of American Indians, activists and veterans from across the country have gathered to block the $3.78 billion Dakota Access Pipeline before it reaches the Missouri River near the Standing Rock reservation. "We been here since the beginning of time. We ain't going nowhere."

The Corps' statement may not halt construction; it could merely result in fines against the pipeline company if work continues. The company constructing the pipeline, Dallas-based Energy Transfer Partners, and the Morton County Sheriff's Office didn't have immediate comment.

Thousands of veterans traveled to frigid North Dakota this weekend to support protesters, who have clashed violently with law enforcement in recent weeks.

It was unclear what effect, if any, the Corps' ruling would have on the veterans' planned march on Monday.

For activists, it was a joyous moment.

"There's songs of victory that are going to be sung tonight," said Lance King, who moved from Minneapolis back to South Dakota's Pine Ridge reservation in August. "They were denied, but they're still going to drill. We're still going to be here." But for now, he said, "I'm just happy. Content."

The Standing Rock Sioux tribe and others argue the pipeline near the reservation threatens a water source and cultural sites.

As evening fell Sunday night, a line of people wound through camp, carrying mirrored shields over their heads.

"We are the silver river, come to kill the black snake," said George Pletnikoff Jr., who traveled to Standing Rock from St. Paul Island, Alaska, using the term the tribes sometimes use to describe the pipeline.

Digging in

The federal and state government have ordered people to leave the main encampment, which is on Army Corps land close to the construction site, by Monday.

Demonstrators are digging in for the winter, and federal, state and local authorities have said they won't forcibly remove them.

The call went out for veterans to come to Standing Rock. They answered this weekend by the thousands.

Gray-haired men crunched through the snow, carrying cold-weather gear from a truck to a military surplus tent where they'll be sleeping.

"These came from all over the world," a volunteer called out, piling boxes of sleeping pads into the arms of a man whose cap identified him as a Vietnam veteran. "You are loved. Thank you, veterans."

Ronald Long, 69, a Vietnam-era Marine and member of Minnesota's Red Lake Band of Chippewa, watched the supply line with a smile.

"Without the water, there will be no eighth generation. Look what we're doing to the Earth," said Long.

He joined others crowding into the sprawling camp filled with tents, tepees, yurts and protest signs.

The four-state, 1,172-mile Dakota Access Pipeline is nearly complete, missing just the miles that skirt the Standing Rock reservation and tunnel under a Missouri river reservoir.

"Our mission … is peace and prayer. We are guests of the Standing Rock tribe and we will conduct ourselves in that manner," said Loreal Black Shawl, an organizer for Veterans Stand for Standing Rock. Black Shawl, an Army veteran and descendant of a survivor of the 1890 Wounded Knee massacre, addressed veterans gathered at Sitting Bull Community College on Saturday. "We will not instigate, we will not do anything to bring any bad karma or press upon our hosts," she said.

Earlier, there were violent clashes with law enforcement — trucks and tires set on fire on a highway bridge, tear gas, water cannons and a young protester injured so badly that she may lose an arm.

Morton County Sheriff Kyle Kirchmeier, after talks with U.S. Attorney General Loretta Lynch and Veterans Stand for Standing Rock organizer Wesley Clark Jr., announced Saturday that law enforcement was willing to pull back from the contested Backwater Bridge — a flash point for protests — if activists and veterans were willing to stay to the south of the bridge on Monday.

"We had a good discussion and walked away with a mutual commitment to maintaining peace, showing mutual respect … and ensuring adequate space between law enforcement and protesters who peacefully exercise their First Amendment rights," Maj. Gen. Alan Dohrmann of the North Dakota National Guard said in a statement.

Anyone trying to cross the bridge, fly drones across it, or flank law enforcement "will show that protesters have chosen to be aggressors by violating the law" and will be arrested, the sheriff's department said on Facebook.

"Bring it on," said Duke Dunn, a Vietnam-era Navy veteran who came limping into Oceti Sakowin, the main protest camp, on a crutch for the knee he twisted photographing a protest march back home in Washington, D.C.

For Chas Jewett, who grew up on the nearby Cheyenne River Sioux reservation, the camp is "like home. There's a genetic memory we have as Indian people, of coming together before. Coming here, you just feel that. You feel what once was, and what can be."

She sat in a warm Mongolian yurt that is a hub for one of the many camps-within-camps — the Women's Camp.

"Everyone is all, like, what's it like to be on the front lines? As Indian women, we've been on the front line of this battle for 500 years," Jewett said. "We're not going to solve the problem by getting to the drill pad and stopping them there. We're going to stop the problem by convincing the hearts and minds of America that this is an unnecessary walk toward destruction."

Oceti Sakowin is a world away from the life Lance King lived as a trucker in Minneapolis. He sat in a tepee, wearing the wapaha, the magnificent feathered headdress passed down to him from his grandfather, Chief Matthew King.

"I know what it is to be an Indian in the city. The traditionalism, the ceremonies, the gatherings are minimal. … Standing Rock is a birthplace of reigniting that faith. Reigniting that lost connection, lost vision," he said. "People say our language is dissipating, our language is dying. No, it's not. 'Our culture is dying.' No it's not. … We were a sleeping giant, and now I'm awake."

Sharing resources

King wore a pair of new Sorrell boots someone donated to the camp. As dollars and donations poured into Standing Rock, beleaguered law enforcement officers shivering on the other side of the line put out a call for support as well, asking for warm hats and gloves, granola bars, energy drinks and soda pop.

Standing Rock activists saw the request and responded, ferrying supplies north to the sheriff's office in Mandan on Friday. An officer, clad in riot gear, accepted the donation.

"Thanks, guys," he said.

"We're going to give them everything they want, except the soda, except the energy drink, because it's not healthy for them," said Andre Perez, who traveled from Hawaii to come to Standing Rock. "We're going to give them water instead, because water is life."

The Associated Press contributed to this report.

Jennifer Brooks • 612-673-4008