By Timothy Mclaughlin

March 21 (Reuters) - A stretch of North Dakota highway closed by months of protests against the Dakota Access pipeline was to re-open on Tuesday, law enforcement officials said, a day after the pipeline operator said oil could move through it soon.

Energy Transfer Partners LP, according to court documents filed on Monday, believes oil could begin flowing through the 1,172-mile (1,885-km) pipeline as early as this week.

Traffic would be allowed on Highway 1806 from Fort Rice, south of Mandan in the state's southwest, to the Cannonball Bridge near the Standing Rock Sioux reservation starting at noon, the Morton County Sheriff's Department and North Dakota Highway Patrol said in a statement.

The nearly 9-mile (14 km) stretch of highway was closed in October when Native Americans and environmental activists descended on the area in an effort to force the re-routing of the multibillion dollar pipeline away from a lake upstream from the reservation.

The demonstrators said the pipeline could pollute water supplies and destroy sacred historic tribal sites. Backwater Bridge was the site of multiple clashes between law enforcement and protesters and barricades were erected on it to keep protesters from reaching the site of the pipeline.

The remaining barricades were being removed on Tuesday, authorities said. Heavy snow also fell over the area during the winter.

Law enforcement swept through the protest camp late last month, clearing the remaining protesters.

Earlier this month, a federal judge denied a request by a Native American tribe for an emergency injunction to prevent oil flowing through part of pipeline, saying such a move would be against the public interest.

(Reporting by Timothy Mclaughlin in Chicago; Editing by Dan Grebler)