CANNON BALL, North Dakota —The secretary of the Army Corps of Engineers has turned down a permit for a controversial pipeline project running through North Dakota, in a victory for Native Americans and climate activists.

A celebration erupted following the Sunday announcement at the main protest camp in Cannon Ball, North Dakota, where the Standing Rock Sioux tribe and others have been protesting against the 1,172-mile Dakota Access Pipeline for months.

However it may prove to be a short-lived victory because President-elect Donald Trump has said he supports the project and policy experts believe he could reverse the decision if he wanted to.

The line, owned by Texas-based Energy Transfer Partners LP , had been complete except for a segment planned to run under Lake Oahe, a reservoir formed by a dam on the Missouri River.

That stretch required an easement from federal authorities. The Obama administration delayed a decision on the permit twice in an effort to consult further with the tribe.

Standing Rock Sioux Chairman Dave Archambault II told NBC News that he was "thankful that there were some leaders in the federal government that realized that something is not right even though it's legal."

"This is something that will go down in history, and I know that it's a blessing for all indigenous peoples," he said.

The Army Corps assistant secretary for civil works, Jo-Ellen Darcy, said in the statement Sunday: "Although we have had continuing discussion and exchanges of new information with the Standing Rock Sioux and Dakota Access, it's clear that there's more work to do.

"The best way to complete that work responsibly and expeditiously is to explore alternate routes for the pipeline crossing."

Related: 'Water Is Life': A Look Inside the Dakota Access Pipeline Protesters' Camp

Cheers broke out as word spread through the protest camp in Cannon Ball. Federal officials had given activists, who include Native American tribe members and non-members alike, a deadline of Monday to vacate the camp because of worries about the plunging temperatures.

But Energy Transfer Partners, the company behind the project, denounced the decision Sunday night as "a purely political action."

"The White House's directive today to the Corps for further delay is just the latest in a series of overt and transparent political actions by an administration which has abandoned the rule of law in favor of currying favor with a narrow and extreme political constituency," it said in a statement.

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The planned route for the pipeline would have run within a half-mile of the Standing Rock Sioux reservation, crossing beneath the Missouri River. Opponents had said the pipeline would adversely affect drinking water and disturb sacred tribal sites.

The Obama administration several times asked that Energy Transfer Partners stop construction. But the installation of hyper-beam lights there last month showed that the request was rejected.

Attorney General Loretta Lynch said in a statement that the Justice Department "remains committed to supporting local law enforcement, defending protestors' constitutional right to free speech and fostering thoughtful dialogue on the matter."

Former presidential candidate Bernie Sanders said in a statement: "I appreciate very much President Obama listening to the Native American people and millions of others who believe this pipeline should not be built."

But Sen. Heidi Heitkamp, D-North Dakota, said the decision did not come soon enough.

"This administration's delay in taking action — after I've pushed the White House, Army Corps, and other federal agencies for months to make a decision — means that today's move doesn't actually bring finality to the project. The pipeline still remains in limbo," Heitkamp said in a statement Sunday.

Meanwhile, Sen. John Hoeven, R-North Dakota, said the decision"violates the rule of law and fails to resolve the issue. Instead, it passes the decision off to the next administration, which has already indicated it will approve the easement, and in the meantime perpetuates a difficult situation for North Dakotans."

And House Speaker Paul Ryan called the ruling "big-government decision-making at its worst" on Twitter.