WASHINGTON (Reuters) - The U.S. Army Corps of Engineers will grant the final approval needed to finish the Dakota Access Pipeline project, U.S. Senator John Hoeven and Congressman Kevin Cramer of North Dakota said on Tuesday.

Opponents of the Dakota Access oil pipeline rally outside the Bank of North Dakota in Bismarck, North Dakota, U.S., January 31, 2017. REUTERS/Terray Sylvester

However, opponents of the $3.8 billion project, including the Standing Rock Sioux Tribe, whose reservation is adjacent to the route, claimed that Hoeven and Cramer were jumping the gun and that an environmental study underway must be completed before the permit was granted.

For months, climate activists and the Standing Rock Sioux tribe have been protesting against the completion of the line under Lake Oahe, a reservoir that is part of the Missouri River. The one-mile stretch of the 1,170-mile (1,885 km) line is the only incomplete section in North Dakota.

The project would run from the western part of the state to Patoka, Illinois, and connect to another line to move crude to the U.S. Gulf Coast.

Hoeven said Acting Secretary of the Army Robert Speer had told him and Vice President Mike Pence of the move. “This will enable the company to complete the project, which can and will be built with the necessary safety features to protect the Standing Rock Sioux Tribe and others downstream,” Hoeven, a Republican, said in a statement.

Representatives for the Army Corps of Engineers could not be reached immediately for comment late on Tuesday. The Department of Justice declined to comment.

President Donald Trump signed an executive order last week allowing Energy Transfer Partners LP’s Dakota Access Pipeline to go forward, after months of protests from Native American groups and climate activists pushed the administration of President Barack Obama to ask for an additional environmental review of the controversial project.

The approval would mark a bitter defeat for Native American tribes and climate activists, who successfully blocked the project earlier and vowed to fight the decision through legal action.

On Tuesday evening, the Standing Rock tribe said the Army could not circumvent a scheduled environmental impact study that was ordered by the outgoing Obama administration in January. “The Army Corps lacks statutory authority to simply stop the EIS,” they said in a statement.

The tribe said it would take legal action against the U.S. Army’s reported decision to grant the final easement.

“JUMPED THE GUN”

Jan Hasselman, an Earthjustice lawyer representing the tribe, told Reuters that Hoeven and Cramer “jumped the gun” by saying the easement would be granted and that the easement was not yet issued.

Dallas Goldtooth of the Indigenous Environment Network, which has been a vocal opponent of the pipeline, said on Twitter that lawmakers were “trying to incite violence” by saying the easement was granted before it was official.

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There have been numerous clashes between law enforcement and protesters over the past several months, some of which have turned violent. More than 600 arrests have been made.

Heavy earth-moving equipment had been moved to the protest camp in recent days to remove abandoned tipis and cars, with the camp to be cleared out before expected flooding in March.

There were more than 10,000 people at the camp at one point, including Native Americans, climate activists and veterans. Several hundred remain.

A spokesman for Hoeven, Don Canton, said it would probably be a “matter of days rather than weeks” for the easement to be issued.

Oil producers in North Dakota are expected to benefit from a quicker route for crude oil to U.S. Gulf Coast refineries.

North Dakota Democratic Senator Heidi Heitkamp said the timeline for construction was still unknown but said she hoped Trump would provide additional law enforcement resources and funding to ensure the safe start of pipeline construction.

“We also know that with tensions high, our families, workers, and tribal communities deserve the protective resources they need to stay safe,” Heitkamp said.