The US Army Corps of Engineers on Sunday announced they will no longer allow the Dakota Access Pipeline to cross under a river near the Standing Rock reservation in North Dakota, marking a huge win for Native Americans and protesters who had long opposed the construction.

"Today, the US Army Corps of Engineers announced that it will not be granting the easement to cross Lake Oahe for the proposed Dakota Access Pipeline," Standing Rock Sioux Tribal Chairman Dave Archambault II said in a statement sent to BuzzFeed News. "Instead, the Corps will be undertaking an environmental impact statement to look at possible alternative routes.

"We wholeheartedly support the decision of the administration and commend with the utmost gratitude the courage it took on the part of President Obama, the Army Corps, the Department of Justice, and the Department of the Interior to take steps to correct the course of history and to do the right thing."

"It took tremendous courage to take a new approach to our nation-to-nation relationship, and we will be forever grateful," he said.

Assistant Army Secretary for Civil Works Jo-Ellen Darcy said she based her decision on a need to explore alternate pipeline routes.

"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," Darcy said in a statement. "The best way to complete that work responsibly and expeditiously is to explore alternate routes for the pipeline crossing."

Energy Transfer Partners, the company building the pipeline, released a statement saying it was still committed to building under the river.

"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," the company said.