By Timothy Gardner

WASHINGTON (Reuters) – A U.S. federal judge denied a request by Native American tribes seeking a halt to construction of the final link in the Dakota Access Pipeline on Monday, the controversial project that has sparked months of protests from tribal activists seeking to halt the 1,170-mile line.

Judge James Boasberg of the U.S. District Court in Washington, D.C., at a hearing, rejected the request from the Standing Rock Sioux and Cheyenne River Sioux tribes, who had argued that the project will prevent them from practicing religious ceremonies at a lake they say is surrounded by sacred ground.

The U.S. Army Corps of Engineers last week granted a final easement to Energy Transfer Partners LP, the company building the $3.8-billion Dakota Access Pipeline (DAPL), after President Donald Trump issued an order to advance the pipeline days after he took office in January.

Lawyers for the Cheyenne River Sioux and the Standing Rock Sioux wanted Judge Boasberg to block construction with a temporary restraining order.

“We are contending that the waters of Lake Oahe are sacred to Cheyenne River and all of its members, and that the very presence of a pipeline, not only construction but possible oil flow through that pipeline, would obstruct the free exercise of our religious practices,” Matthew Vogel, a legislative associate for the Cheyenne River Sioux, told reporters in a conference call ahead of the hearing.

The company only needs to build a final 1,100-foot (335 meter) connection in North Dakota under Lake Oahe, part of the Missouri River system, to complete the pipeline.

The line is set to run from oilfields in the Northern Plains of North Dakota to the Midwest, and then to refineries along the Gulf of Mexico, could be operating by early May.

Chase Iron Eyes, a member of the Standing Rock Tribe, said in the call that the pipeline would also cause economic harm to Native Americans.

The tribes could be facing a difficult task in convincing Boasberg to grant the restraining order. Last September, he rejected a broad request by Native Americans to block the project. That ruling was superseded by the Obama Administration, which delayed the line, seeking more environmental review.

Thousands of tribe members and environmental activists have protested the pipeline setting up camps last year on Army Corps land in the North Dakota plains. In December, the Obama Administration denied ETP’s last needed permit, but with Trump’s stated support of the pipeline, that victory was short-lived for the Standing Rock Sioux.

The Army Corps has said it will close remaining camps on federal lands along the Cannonball River in North Dakota after Feb. 22.

Cleanup efforts continued in the main protest camp located on federal land over the weekend. Only a few hundred protesters remain, and crews have been removing tipis and yurts. The Standing Rock tribe has been asking protesters to leave.

(Reporting by Timothy Gardner; additional reporting by Terray Sylvester in Cannon Ball, North Dakota; Editing by Nick Zieminski)