"For 136 years, under the 1872 (Mining Act), valuable minerals mined on federal lands have been given to private interests for free. By comparison, other extractive industries -- oil, gas, coal -- pay a royalty when operating on public lands," the senators wrote.

The letter was signed by Sens. Russ Feingold, D-Wis.; John Sununu, R-N.H.; Maria Cantwell, D-Wash.; Judd Gregg, R-N.H.; Jack Reed, D-R.I.; Sheldon Whitehouse, D-R.I.; Bob Menendez, D-N.J.; Olympia Snowe, R-Maine; Ben Cardin, D-Md., and Bernard Sanders, an Independent from Vermont.

Last November, the House voted 244-166 for a bill calling for an 8 percent royalty on the gross income of new hard-rock mines on federal land and a 4 percent royalty on mines already operating on federal property.

All three of Nevada's representatives in the House voted against the bill, and Sens. Harry Reid, D-Nev., and John Ensign, R-Nev., both declared the House bill "dead" in the Senate.

The Senate Energy and Natural Resources Committee has conducted two hearings on mining reform since last September, but a Senate version of the mining reform bill has not yet been introduced.

Bill Wicker, a committee spokesman, acknowledged progress has been slow.

"A great deal of high-level staff time has gone into drafting legislation, and we're continuing to work on it every day," Wicker said. "We're also aware that the election year calendar is not an ally."

It is unlikely mining reform will go anywhere in the Senate without the nod of Reid, the Senate majority leader.

"If we are able to pass mining law reform, it's going to have to be a package that provides a fair return to taxpayers and that gives miners and mining communities the certainty they need and deserve," Reid spokesman Jon Summers said.

Ensign said he would support "reasonable" reform that would not cripple the mining industry.

"We are already suffering at the gas pump today by allowing ourselves to become too reliant on foreign sources of oil," Ensign said. "Are we really prepared to make the same mistake with our domestic mining industry?"

Contact Stephens Washington Bureau reporter Tony Batt at tbatt@stephensmedia.com or 202-783-1760.