The US Army Corps of Engineers has turned down a permit for a controversial pipeline project running through North Dakota, according to a statement released on Sunday, a victory for Native Americans and climate activists who have protested against the project for several months.

The 1,172-mile Dakota Access Pipeline, 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.

“The Army will not grant an easement to cross Lake Oahe at the proposed location based on the current record,” a statement from the US Army said.

Assistant Secretary of the Army Jo-Ellen Darcy added in a separate statement: “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 Standing Rock Sioux tribe, along with climate activists, have been protesting the $3.8 billion project, saying it could contaminate the water supply and damage sacred tribal lands. The protest has garnered support from thousands who have flocked to North Dakota to protest against the completion of the line.

Protest organizers had for months argued that crossing the Missouri River adjacent to the Standing Rock Sioux Reservation presented a danger to their water source. Protests grew over the months, with hundreds of veterans flocking to the camp in recent days to stand against what they say are aggressive tactics from law enforcement.

The department of the Army announced in November it was delaying the decision to grant the easement for the pipeline after the protests gained national attention.

Standing rock

Foto: The Oceti Sakowin camp seen in a snowstorm during a protest against plans to pass the Dakota Access pipeline near the Standing Rock Indian Reservation, near Cannon Ball, North Dakota, on November 29.sourceREUTERS/Stephanie Keith

In a statement, Standing Rock Sioux chairman Dave Archambault celebrated the announcement, saying the tribe will be "forever grateful" the US government acknowledged its concerns.

"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," the statement read.

"The Standing Rock Sioux Tribe and all of Indian Country will be forever grateful to the Obama Administration for this historic decision," it continued.