Dakota Access has been waiting months for approval of a final easement from the corps to cross the river. The U.S. Department of the Army announced yesterday that it would delay issuing the easement in order to further consult with the tribe.

The companies contend that the corps has already granted all of the relevant authorizations when it approved the permit for the river crossing.

"Dakota Access Pipeline has waited long enough to complete this pipeline. Dakota Access Pipeline has been granted every permit, approval certificate and right-of-way needed for the pipeline's construction. It is time for the courts to end this political interference and remove whatever legal cloud that may exist over the right-of-way beneath federal land at Lake Oahe," Energy Transfer Partners CEO Kelcy Warren said in a statement.

In its statement Monday, the corps said a review of previously granted permits followed legal requirements, which Energy Transfer Partners said "should have brought the unwarranted delay to a close."

"Without even identifying any specific problem with its almost three-year review or the record it was based upon, the Army has now determined that 'additional discussion with the Standing Rock Sioux Tribe and analysis are warranted," the companies said in a statement.