Senior Democrats on Tuesday suggested that they may use appropriations legislation to block Bush administration plans to make sweeping changes to the 1973 Endangered Species Act.

A draft Interior Department rule, leaked Tuesday by two environmental groups, would limit the reach of the law (PL 93-205), which prohibits industrial and other activities that could harm the habitats of endangered and threatened species.

The proposal is still undergoing an interagency review, but environmentalists argue that it could allow problematic industrial practices to continue, limit the listing of new endangered species and transfer too much authority to state governments.

A spokesman for the Interior Department’s Fish and Wildlife Service said the leaked proposal is an early draft that will be revised extensively.

Experts say the rule would have to be officially proposed within the next six weeks if the administration wants it in place before President Bush leaves office.

Interior Secretary Dirk Kempthorne, who sponsored legislation to overhaul the law when serving in the Senate (1993-99), said last week that the department was taking thousands of public comments to see “what can we do so it gets closer and closer to meeting the original intent of the act.”

But with details of the plan emerging Tuesday, several key Democrats vowed to block it.

House Natural Resources Chairman Nick J. Rahall II, D-W.Va., said the fiscal 2008 Interior-Environment appropriations bill could be a vehicle to block the administration’s efforts.

“That type of dismantling of the [Endangered Species Act], that was attempted in the past and sounds like is being attempted in a backdoor fashion by this administration, needs to stop,” said Rahall.

Similarly, Democratic Reps. James P. Moran of Virginia and Maurice D. Hinchey of New York, who both serve on the Interior-Environment Appropriations Subcommittee, said Congress may have to intervene to stop the rule.

“The executive branch of the government does not have the authority to make the law or compromise existing laws,” Hinchey said. “If they try to push this kind of thing, we’re going to have to step in aggressively and stop them from doing it.”

Appropriations bills can block a federal regulation by ordering an agency not to spend any money on implementing the rule.

For years, farmers, industry groups and private-property advocates have said the requirements of the Endangered Species Act are too rigid and have led to only a handful of successes in recovering species. About 80 percent of the species protected by the law live on private lands.

Rick Krause, senior director of regulatory relations for the American Farm Bureau, says the requirements need to be more flexible for farmers, whose livelihoods can be drained if a federal agency seeks to implement endangered species rules on their land.

Former Rep. Richard W. Pombo, R-Calif. (1993-2007), and other private-property advocates repeatedly have come up short in pushing wholesale changes to the law through Congress. Pombo’s attempts, which had Bush administration support, typically passed in the House but died in the Senate.

With Democrats in control of the Capitol and Pombo having lost his 2006 re-election race, there is virtually no chance of moving similar legislation through this Congress.

Environmentalists said the Bush administration’s proposal is an attempt to make an end-run around Congress.

“It’s another abuse of executive authority,” said Daniel Patterson, Southwest director of the Public Employees for Environmental Responsibility, which along with the Center for Biological Diversity obtained copies of the draft proposal from a federal official.