BISMARCK, N.D. –  The company building the Dakota Access oil pipeline wants a federal judge to block the U.S. Army Corps of Engineers from launching a full environmental study of the $3.8 billion pipeline's disputed crossing of a Missouri River reservoir in North Dakota.

Texas-based Energy Transfer Partners asked U.S. District Judge James Boasberg on Tuesday to stop the Corps from publishing a notice in the Federal Register on Wednesday announcing the study. ETP wants any further study put on hold until Boasberg, in Washington, D.C., rules on whether ETP already has the necessary permission to lay pipe under Lake Oahe — the reservoir that's the water source for the Standing Rock Sioux tribe.

ETP wants to block further study so that the decision on the permitting, which is likely weeks away, will be "free from the risk that its ruling will be frustrated or thwarted by new governmental actions." The Corps did not immediately respond to ETP's request.

The stretch under Lake Oahe is the last big chunk of construction for the 1,200-mile pipeline. The Corps wants to look at alternate routes, the potential for a pipeline leak and tribal treaty rights in the wake of opposition by the Standing Rock Sioux and its supporters who believe a pipeline leak would contaminate the tribe's drinking water.

ETP maintains the pipeline is safe and that the Corps gave it permission in July to proceed with the Lake Oahe stretch, but the Corps says all of the necessary steps have not yet been completed — including an easement to work on federal land and the notification of Congress.