The Acting Secretary of the Army has directed the Army Corps of Engineers to proceed with an easement necessary to complete the Dakota Access pipeline, North Dakota Sen. John Hoeven said on Tuesday.

Hoeven issued a statement late in the evening after he said Acting Army Secretary Robert Speer informed him of the decision. Hoeven said he also spoke with Vice President Mike Pence.

A spokesman for the U.S. Army did not immediately respond to requests for comment Tuesday night. Hoeven spokesman Don Canton says that Speer's move means the easement "isn't quite issued yet, but they plan to approve it" within days.

The crossing under Lake Oahe, a wide section of the Missouri River in southern North Dakota, is the final big chunk of work on the four-state, $3.8 billion pipeline to carry North Dakota oil through South Dakota and Iowa to Illinois. President Donald Trump on Jan. 24 called on the Army Corps of Engineers to reconsider its December decision to withhold permission until more study is done on the crossing.

The move is likely to be challenged in court by the Standing Rock Sioux, who have spent months protesting the project along with supporters from around the country. The tribe gets drinking water from the river and worries a pipeline leak would pollute the water. The developer, Texas-based Energy Transfer Partners, says the pipeline is safe.

An environmental assessment conducted last year determined the crossing would not have a significant impact on the environment. However, then-Assistant Army Secretary for Civil Works Jo-Ellen Darcy on Dec. 4 declined to issue an easement, saying a broader environmental study was warranted in the wake of opposition by the Standing Rock Sioux. The tribe gets its drinking water from the lake and worries a pipeline leak would pollute the water.

The company says the pipeline is safe. It called Darcy's decision politically motivated and accused then-President Barack Obama's administration of delaying the matter until he left office. Two days before he left the White House, the Corps launched a study of the crossing that could take up to two years to complete.

President Donald Trump on Jan. 24 — just four days after he took office — signed an executive action telling the Corps to quickly reconsider the Dec. 4 decision.

The company appears poised to begin drilling under the lake immediately. Workers have already drilled entry and exit holes for the Oahe crossing, and the company has put oil in the pipeline leading up to the lake in anticipation of finishing the project, its executive vice president Joey Mahmoud said in court documents filed earlier this month.

Hundreds and at times thousands of pipeline opponents who have dubbed themselves "water protectors" have camped on federal land near the crossing site since last August, often clashing with police and prompting more than 625 arrests. The camp's population has thinned to fewer than 300 due to harsh winter weather and a plea by Standing Rock Chairman Dave Archambault for the camp to disband before the spring flooding season.