DENVER — The clash over expanding oil and gas drilling in the West will play out in federal court this week when environmentalists challenge a deal between Utah and the Interior Department on proposed wilderness areas that critics argue sacrifices the region's pristine areas for unbridled development.

The case before the 10th U.S. Circuit Court of Appeals in Denver stems from a 2003 agreement that settled a lawsuit by the state of Utah. The state opposed protecting federal land proposed by the public for wilderness designation.

The deal, though, reaches far beyond Utah; it applies to millions of acres throughout the West previously shielded from development while advocates lobbied for permanent protection.

"This affects millions of acres of our most pristine, remote wild lands in very fundamental ways for years to come," said Jim Angell, a lawyer with the Denver office of Earthjustice, which will represent several environmental groups in a hearing Wednesday in the federal appeals court.

Environmentalists argue that the agreement signed by former Utah Gov. Mike Leavitt and Interior Secretary Gale Norton was an end-run around federal laws and left the public out of the discussion.

"It's undemocratic. It's not how public lands should be managed," said Heidi McIntosh, conservation director for the Southern Utah Wilderness Alliance.

Since the deal was struck, oil and gas companies have leased some of the tracts overseen by the Bureau of Land Management in Utah and western Colorado. Land proposed as wilderness by various groups and Rep. Diana DeGette, D-Colo., sit atop some of the largest natural gas reserves in the country.

Areas in dispute include red rock canyon country near the Colorado River in western Colorado and eastern Utah.

"I think that everyone understands that the Department of Interior's No. 1 priority is development of oil and gas, no matter the cost," McIntosh said.

Federal officials, however, insist that the BLM is charged with managing the public land for multiple uses. They say the Utah settlement is in line with federal law and the Clinton administration overstepped its authority when it declared that some land should be managed as wilderness until Congress made a decision.

Industry representatives have expressed frustration with the issue, saying they get caught in the middle.

"For us, minerals are where they are. We can't move them to where they don't overlay any other resource," said Drew Bower, vice president of the Petroleum Association of Wyoming, a trade group.

She noted that the lands environmentalists are trying to protect were passed over when Congress in the 1970s gave the BLM 15 years to inventory its land and recommend parcels that should be federal wilderness, which is off-limits to roads, development and motorized vehicles.