Montana Gov. Brian Schweitzer is asking the White House to reject calls for more water releases from reservoirs on the Missouri River to ease drought conditions downstream.
Elected officials from states along the Mississippi River this week said the additional releases are needed to keep vital barge traffic moving in coming months.
But Schweitzer says sending more water down the Missouri would be a "knee-jerk, illegal reaction" to the problems on the Mississippi.
He wrote in a Wednesday letter to President Barack Obama that such a move would undermine the Army Corps of Engineers as it manages the river for the long-term.
Corps officials started reducing Missouri River releases from South Dakota's Gavins Point Dam last week, saying the move is needed to protect recreation and hydropower on the river.