Wyoming will get a say over whether the Yellowstone River is given a special federal designation.
Interior Department officials had said that the river might be considered a candidate for the National Blueways System, which is designed to promote conservation and recreation on rivers.
Wyoming's congressional delegation voiced concern that such a designation could limit the river's use.
Sens. Mike Enzi and John Barrasso and Rep. Cynthia Lummis had previously said the National Blueways System was a federal power grab.
But in a statement this week, they said that they received a letter from U.S. Interior Secretary Ken Salazar that promised rivers won't get the federal designation unless states first OK it.
The Yellowstone River has its headwaters in Wyoming.