LEWISTON, Idaho -

Two conservation groups have filed a 60-day notice of intent to sue the federal government over a plan to expand and repair a backcountry airstrip in northern Idaho.

Wilderness Watch and the Friends of the Clearwater sent the notice Monday to the U.S. Forest Service, U.S. Fish and Wildlife Service and two other agencies.

The groups tell the Lewiston Tribune that the expansion of Fish Lake Airstrip in the Selway-Bitterroot Wilderness Area will harm threatened bull trout.

The groups say habitat degradation and increased fishing pressure at Fish Lake will result from lengthening the runway by about 350 feet.

The groups say federal agencies need to do a biological assessment before doing the work, and that airstrip improvements could affect the area's wilderness character.