WASHINGTON — Parts of the Endangered Species Act may soon be extinct.

The Bush administration wants federal agencies to decide for themselves whether highways, dams, mines, and other construction projects might harm endangered animals and plants. New regulations, which don’t require the approval of Congress, would reduce the mandatory, independent reviews government scientists have been performing for 35 years, according to a draft first obtained by the Associated Press.

Interior Secretary Dirk Kempthorne said late yesterday the changes were needed to ensure that the Endangered Species Act would not be used as a “back door” to regulate the gases blamed for global warming. In May, the polar bear became the first species declared as threatened because of climate change. Warming temperatures are expected to melt the sea ice the bear depends on for survival.

The draft rules would bar federal agencies from assessing the emissions from projects that contribute to global warming and its effect on species and habitats.

“We need to focus our efforts where they will do the most good,” Mr. Kempthorne said in a news conference organized quickly after AP reported details of the proposal. “It is important to use our time and resources to protect the most vulnerable species. It is not possible to draw a link between greenhouse gas emissions and distant observations of impacts on species.”

If approved, the changes would represent the biggest overhaul of endangered species regulations since 1986. They would accomplish through rules what conservative Republicans have been unable to achieve in Congress: ending some environmental reviews that developers and other federal agencies blame for delays and cost increases on many projects.

The chairman of the House Natural Resources Committee, which oversees the Interior Department, said he was “deeply troubled” by the changes.

“This proposed rule … gives federal agencies an unacceptable degree of discretion to decide whether or not to comply with the Endangered Species Act,” Rep. Nick Rahall, a Democrat of West Virginia, said. “Eleventh-hour rulemakings rarely if ever lead to good government.”

The new regulations follow a pattern by the Bush administration not to seek input from its scientists. The regulations were drafted by attorneys at both the Interior and Commerce Departments. Scientists with both agencies were first briefed on the proposal last week during a conference call, according to an official who asked not to be identified.

Last month, in similar fashion, the Environmental Protection Agency surprised its scientific experts when it decided it did not want to regulate greenhouse gases under the Clean Air Act.

The rule changes unveiled yesterday would apply to any project a federal agency would fund, build or authorize that the agency itself determines is unlikely to harm endangered wildlife and their habitat. Government wildlife experts currently participate in tens of thousands of such reviews each year.

The revisions also would limit which effects can be considered harmful and set a 60-day deadline for wildlife experts to evaluate a project when they are asked to become involved. If no decision is made within 60 days, the project can move ahead.

“If adopted, these changes would seriously weaken the safety net of habitat protections that we have relied upon to protect and recover endangered fish, wildlife and plants for the past 35 years,” executive director of the National Wildlife Federation’s Wildlife Conservation and Global Warming initiative, John Kostyack, said.

Under current law, federal agencies must consult with experts at the Fish and Wildlife Service or the National Marine Fisheries Service to determine whether a project is likely to jeopardize any endangered species or to damage habitat, even if no harm seems likely. This initial review usually results in accommodations that better protect the 1,353 animals and plants in America listed as threatened or endangered and determines whether a more formal analysis is warranted.

The Interior Department said such consultations are no longer necessary because federal agencies have developed expertise to review their own construction and development projects, according to the 30-page draft obtained by the AP.