OKLAHOMA CITY (AP) - The Chickasaw and Choctaw nations have sued to keep a state agency from selling and exporting water from a southeast Oklahoma reservoir without first reaching agreements with the tribes.

The lawsuit filed Thursday seeks to stop the Oklahoma Water Resources Board from selling water storage rights to Sardis Lake to the Oklahoma City Water Utility Trust. Oklahoma City receives water from the reservoir, which is located within both tribes' territories.

The lawsuit says the tribes have longstanding treaties with the federal government regarding water resources ownership, but they haven't been included in negotiations between the board and the trust.