BISMARCK, N.D. (AP) — The federal government says regulations prevent it from even considering a request by U.S. Sen. Heidi Heitkamp to extend a corn planting deadline to ease farmers’ insurance concerns in North Dakota.

The U.S. Department of Agriculture’s Risk Management Agency said in a statement Wednesday that it is prohibited from changing the May 25 deadline set for most counties in the state. Crop insurance policies are agreements struck between approved providers and farmers, and any changes in those contracts would have to have been made by Nov. 30 last year.