"Environmental issues such as mining-specific water standards, cleanup standards" and the ability to stop operations in mines even after they have passed environmental tests "are all out of the rule," Lexi Shultz, director at the Mineral Policy Center in Washington, told Reuters.

The Bush administration said earlier this year it would keep the rule requiring mining companies to post bonds to cover clean-up costs. Without the bonding requirement, taxpayers could eventually pay more than $1 billion in potential clean-up costs for the mines.

But the centerpiece of the new regulations - giving the Interior secretary the power to block mining projects likely to cause "sustainable and irreparable" harm to the land - is in danger.

Larry Finfer, a spokesman for the Interior Department's Bureau of Land Management, said the new provisions cover several issues. "There is much more" to the revisions than simply removing the agency's ability to veto a proposed mining project, he said.

The rollback is a blow to environmentalists who celebrated the Clinton-era rule as the first significant reform to mining regulations in two decades.

The planned regulation also would have replaced an antiquated 1872 rule that gave mining companies the power to reshape land in order to remove ores, and does not subject their gains to federal taxes.

The previous administration had aimed to control such things as cyanide leaching that occurs in the process of extracting gold ore. Hard-rock mining can also pollute water and soil with such heavy metals as cadmium, lead and arsenic.

U.S. mining companies said they hoped the rewritten plan would be more realistic.

The Clinton-era rules "would have created a cumbersome type of regulatory scheme that duplicated existing rules," said Newmont Mining Corp spokesman Doug Hock.

"The industry hasn't had a problem with tougher rules (such as bonding requirements) as long as they make sense in a regulatory context," he said.

The industry has also cited a 1999 National Academy of Sciences study that concluded most U.S. mining regulations were adequate and simply needed to be better implemented.

Green groups say the Bush administration's revisions will make it impossible to define how much work mining companies need to do to repair environmental damage from chemicals after a mine is closed.

And without specific standards, it will be difficult to define how much of a bond companies will need to post to cover the clean-up, they argue.