The senators said the bill, sponsored by Sen. Bob Bennett and Rep. Jim Matheson, would harm wild lands near Zion National Park and in the Mojave Desert.

Bennett has said he hopes to package the Washington County bill with similar legislation that Senate Majority Leader-elect Harry Reid, D-Nev., is sponsoring to manage lands in White Pine County and tack them onto one of the spending bills Congress is trying to pass by the end of the year.

"These public lands are an irreplaceable national asset - wild and unspoiled, rich in archeology and paleontology, and home to many threatened and endangered species," the senators wrote.

The letter was signed by incoming Deputy Senate Majority Leader Richard Durbin, Ill., and Sens. Russ Feingold, Minn.; Robert Menendez, N.J.; Joe Lieberman, Conn.; Hillary Clinton, N.Y.; Frank Lautenberg, N.J.; John Kerry, Mass., and Maria Cantwell, Wash.

All are Democrats except Lieberman, who is an independent.

"In addition to denying wilderness protection for the deserving landscape, [the bill] would threaten proposed wilderness in the region by inviting significant new development on public lands and mandating the sale of tens of thousands of acres of BLM lands without the benefit of full BLM and public review and input," the senators wrote.

A Bennett spokeswoman could not be reached for comment on Wednesday.

The senator has said he doesn't like the practice of passing legislation as part of major, must-pass spending bills, but he will do it if the opportunity arises.

The Washington County bill seeks to settle a series of land-use issues in the rapidly growing county.

It protects 219,725 acres of wilderness, most of it in Zion National Park, designates the Virgin River as the state's first Wild and Scenic River, and designates various utility corridors and rights of way.

It also directs the Interior Department to sell off up to 24,300 acres of federal land in two stages between the passage of the bill and January 2013.

Opponents argue that is too much land to sell, and the bill doesn't protect enough wilderness.

Glenn Rogers, chairman of the Shivwits Band of Paiute Indians, has also asked Sens. John McCain, R-Ariz., and Byron Dorgan, D-N.D., the leaders of the Senate Indian Affairs Committee, to resist the bill.

Rogers said the tribe was not adequately consulted on the legislation, which could create a right of way through the tribe's land, spur more off-road vehicle traffic, and sell off culturally sensitive areas.

"I think it's helpful to get people on record," said Pete Downing, legislative director for the Southern Utah Wilderness Alliance. "The hope is that the more members who are on record the stronger Durbin's hand will be when he goes to the key players and says 'I'm not the only one concerned.' "

Downing said opponents to the bill are only asking that it not be passed in the flurry of activity in Congress in the last days of the session. "Hopefully that's not too much to ask," he said.