(Reuters) – North Dakota’s governor activated 100 National Guard troops on Thursday ahead of an expected ruling by a federal judge on a Native American tribe’s request to halt construction of a crude oil pipeline that has drawn fierce opposition and protests.

The $3.7 billion, 1,100-mile (1,770 km) Dakota Access pipeline would carry oil from just north of land owned by the Standing Rock Sioux Tribe to Illinois, where it would hook up to an existing pipeline and route crude directly to refineries in the U.S. Gulf Coast.

The line would be the first to allow movement of crude oil from the Bakken shale, a vast oil formation in North Dakota, Montana and parts of Canada, to refineries on the U.S. Gulf Coast.

The project has sparked violent clashes between security officers near the construction site and tribe members and other protesters. Opponents say the project will damage burial sites considered sacred to the tribe and pollute the area’s drinking water.

Energy Transfer Partners <ETP.N>, which is leading a group of firms to build the pipeline, did not immediately respond to a request for comment.

Protesters have included actress Shailene Woodley and Green Party presidential candidate Jill Stein. Some have spray-painted construction equipment, attached themselves to bulldozers and broken a fence, local authorities said.

Protests have been held in both North Dakota and Washington, D.C.

In a hearing in federal court in Washington, D.C., earlier this week, U.S. Judge James Boasberg granted in part and denied in part the tribe’s request for a temporary restraining order to stop the project, and said he would decide by Friday whether to grant the larger challenge to the pipeline, which would require the U.S. Army Corps of Engineers to withdraw permits.

In advance of that decision, Governor Jack Dalrymple ordered National Guard troops to the area from bases in Bismarck and two other cities.

Some two dozen troops will help with security at traffic checkpoints – the closest of which is about 30 miles (48 km) from the protest site, said Guard spokeswoman Amber Balken. One hundred troops in all are ready to aid local law enforcement should protests become violent, she said.

“The Guard members will serve in administrative capacities and assist in providing security at traffic information points – the Guardsmen will not be going to the actual protest site,” Balken said.

(Reporting by Eric M. Johnson in Seattle; Editing by Matthew Lewis)