CHEYENNE - Montana's attorney general said Friday that a water agreement with Wyoming protects the decades-old rights of Montana residents to use water from Yellowstone River.

Montana sued Wyoming in the U.S. Supreme Court last year, alleging Wyoming's agriculture and energy industries were using too much water in violation of the Yellowstone River Compact. Montana wants Wyoming to deliver more water in the Tongue and Powder rivers, tributaries of the Yellowstone.

The 1950 agreement, which was approved by Congress, allocated each state a share of water from the Yellowstone and its tributaries. The Tongue and Powder rivers flow through northern Wyoming and southern Montana before draining into the Yellowstone River.

Wyoming Attorney General Bruce Salzburg last month asked the Supreme Court to dismiss the lawsuit, calling it "fundamentally flawed." Wyoming argues that the compact only applied to surface water, while Montana contends that water pumped from underground aquifers for irrigation or during coal-bed methane drilling is covered by the compact.

Montana Attorney General Mike McGrath filed a reply with the Supreme Court on Friday. He said the compact requires that Montana's water uses must be satisfied before Wyoming can use more water.

"Wyoming thinks they can take all the water they want to satisfy their needs," McGrath said. "Our position is that you can't take that water if it shortchanges Montana water users of the water they used prior to 1950."

Salzburg has said Wyoming's construction of reservoirs was encouraged by the compact and that depletion of groundwater by energy and agricultural interests was largely outside the scope of the 1950 agreement.

McGrath said he hopes the Supreme Court will set oral arguments for the case next fall.

Anadarko Petroleum Corp. filed a brief with the Supreme Court last month in support of Wyoming. An Anadarko attorney could not be reached for comment Friday evening.