TUCSON, Ariz. (AP) -- Two conservation organizations are seeking a temporary restraining order to stop construction of a stretch of fencing along the Arizona-Mexico border within a treasured riparian area.

Lawyers for Defenders of Wildlife and the Sierra Club filed a motion Friday in U.S. District Court in Washington seeking to block construction within the San Pedro Riparian National Conservation Area, asking for an appropriate environmental assessment on the impact the fence will have on wildlife and protected federal public lands.

The groups contend that clearing land and putting in an access road along the border and building steel fencing within the corridor of the San Pedro River will harm the biologically diverse waterway, one of the last free-flowing rivers in the southwest.

The river, whose banks are dotted with cottonwood and willow trees, is a seasonal flyway for millions of migratory birds and hosts a large variety of plant and animal life.

A Border Patrol spokesman in Washington did not immediately return a phone call Friday.

The fence construction is part of the Border Patrol's effort to secure the border from illegal immigrant and drug entry. More than 70 miles of primary fencing have been built in Arizona, the busiest point along the Mexican border for such activity.

Matt Clark, a Defenders of Wildlife spokesman in Tucson, said excavation and land clearance work went on within the conservation area this week though not within the river corridor.

Robert Dreher, an attorney for Defenders of Wildlife in Washington, said a judge might not take up the motion until Tuesday.

Dreher said the conservationists predict that there will be damage to the river's flood plain and its ecology if fencing, a roadway and vehicle barriers are built and remain in place.

"All those are things that can be repaired if we get a court order to remove the stuff, but it does seem wasteful," he said.

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