Two of Oklahoma's largest tribal nations in February made a direct threat to sue over the state's high-profile sale of Sardis Lake to Oklahoma City, records show.

Since then, the city has continued Sardis Lake development work that a tribal attorney in February warned was “profoundly unwise” and could spur a lawsuit.

A lawsuit over the Sardis Lake deal would strike at the heart of a decades-old dispute over water rights in Oklahoma, where tribal nations have various treaties for water and other resources that predate statehood.

Amid tribal opposition, the city and state agreed on a $42 million deal last June that gave the city storage rights to 90 percent of Sardis Lake in southeast Oklahoma.