CHEYENNE, Wyo. - Wyoming is seeking to join Utah and Alaska in challenging an Obama administration plan to make millions of acres of undeveloped land in the West eligible for federal wilderness protection.

The state filed papers Thursday asking U.S. District Judge Dee Benson of Utah to let it join in a lawsuit Utah filed last month. Alaska already has moved to join the suit, which challenges the federal "wild lands" policy announced in December.

The policy would restore eligibility for wilderness protection to millions of acres of public lands, reversing a Bush-era approach that opened some Western lands to commercial development. Officials in Utah, Alaska and Wyoming say it would hurt their state's economies by taking federal lands off the table for mineral production and other uses.

Wyoming Gov. Matt Mead said Friday that joining the legal fight is his state's best option. He said he repeatedly has asked U.S. Interior Secretary Ken Salazar t o take the policy off the books, but has not succeeded.

"The order is a de facto wilderness declaration and it could have serious impacts on Wyoming's economy, which depends on the multiple use of the public lands," Mead said.

Chris Tollefson, spokesman for the Interior Department in Washington, said Friday he couldn't comment on Wyoming's move to enter the lawsuit.

In its legal filing, Wyoming points out that the U.S. Bureau of Land Management controls more than 18 million acres in the state.

"The state receives approximately 48 percent of the total mineral revenues generated from BLM lands in Wyoming, which in fiscal year 2010 amounted to nearly $1 billion," the filing said. "Accordingly, any management direction from (Salazar) that takes BLM lands out of multiple use management and treats those lands as wilderness will have a significant economic effect on the state of Wyoming."

Greg Phillips, Wyoming attorney general, declined to comment Friday, saying he couldn't discuss matters that are in court.

In announcing his state's legal challenge last month, Utah Gov. Gary Herbert called the federal plan a "midnight ambush."

Herbert said that while wilderness areas deserve protection, the federal policy would circumvent state efforts to determine what areas should be deemed wilderness and whether such designations would harm his state's economy.

Erik Molvar is a biologist with the Biodiversity Conservation Alliance in Laramie, a group that commonly challenges federal land management decisions on environmental grounds. He said Friday he was disappointed in Wyoming's decision to enter the legal fight.

"The suit claims that the wild lands policy creates de facto wilderness," Molvar said. "But in fact, even if the lands go all the way through the process and get designated as wild lands, you can still have motorized vehicles and other use in them if the agency chooses to manage them that way, and that's very different from de facto wilderness."

And Molvar said only small areas of Wyoming could be affected by the wild lands policy.

"The vast majority of Wyoming's lands are not only available for industrial development already, but a massive amount of public land is already committed to the oil and gas industry through oil and gas leases," Molvar said.

"There is no possibility that the oil and gas industry is going to drill and produce all the oil and gas leases that it has in its hands today in the next 30 or 40 years, so the idea that there could be some threat to the economy is political posturing of a very dishonest kind."