The U.S. Fish and Wildlife Service has given preliminary approval to a land exchange in Alaska that would allow a native-owned energy company to drill for oil on 110,000 acres within the nation’s third largest wildlife refuge along a remote section of the Yukon River.

The deal has the support of Alaska Sen. Ted Stevens, who set a deadline for the agreement in a rider to an appropriations bill pending in Congress.

The land swap not only would allow oil drilling within the 9-million acre Yukon Flats refuge — which borders the more famous Arctic National Wildlife Refuge — it could necessitate the building of roads and a pipeline through wetlands that were nominated in 1987 by Fish and Wildlife for wilderness protection.

Native groups that live near the river oppose the deal because of potential harm to wildlife, including salmon, waterfowl, caribou and moose. Critics also note that the Fairbanks-based oil company has paid millions in fines for dumping toxic waste at drilling sites on Alaska’s North Slope.

“This deal is an open-door invitation to carve out any piece of refuge for commercial gain,” said Jaime Clark, executive vice president of the group Defenders of Wildlife. “It’s really an affront to what it means to be a national wildlife refuge.”

As part of the deal, the U.S. Fish and Wildlife Service would convey land in the middle of the refuge to Doyon Ltd. in return for isolated parcels owned by the company elsewhere within the refuge.