ST. LOUIS (AP) — State versus state battle lines are being drawn across the Mississippi River, with a top Missouri official urging Illinois regulators to back away from a plan that would allow higher levees, potentially worsening flooding on the Missouri side of the river.

Missouri Attorney General Josh Hawley sent a letter last month to the Illinois Department of Natural Resources urging the agency to reconsider a proposed rule change that would deregulate levees and allow those already built too high to remain at the unauthorized level. The letter echoes concerns raised by environmentalists and the U.S. Army Corps of Engineers.

But several Illinois lawmakers and some river interests favor higher levees, citing the increasing frequency of severe floods.