The rules must be published Friday to take effect before Obama is sworn in Jan. 20. Otherwise, he can undo them with the stroke of a pen.
The Interior Department rushed to complete the rules in three months over the objections of lawmakers and environmentalists who argued that they would weaken how a landmark conservation law is applied.
A Nov. 12 version of the final rules obtained by the Associated Press has changed little from the original proposal, despite the more than 250,000 comments received since it was first proposed in August.
The rules eliminate the input of federal wildlife scientists in some endangered species cases, allowing the federal agency in charge of building, authorizing or funding a project to determine for itself if it is likely to harm endangered wildlife and plants.
Current regulations require independent wildlife biologists to sign off on these decisions before a project can go forward, at times modifying the design to better protect species.
The regulations also bar federal agencies from assessing emissions of the gases blamed for global warming on species and habitats, a tactic environmentalists have tried to use to block new coal-fired power plants.
Tina Kreisher, an Interior Department spokeswoman, could not confirm whether the rule would be published before the deadline, saying only that the White House was still reviewing it. But she said changes were being made based on the comments received.
"We started this; we want to finish this," said Kreisher.
If the rules go into effect before Obama takes office, they will be difficult to overturn since it would require the new administration to restart the rule-making process. Congress, however, could reverse the rules through the Congressional Review Act - a law that allows review of new federal regulations.
It's been used once in the last 12 years, but some Democratic lawmakers have said they may employ it to block the endangered species rules and other midnight regulations by the Bush administration.
Rep. Nick Rahall, D-W.Va., chairman of the House Natural Resources Committee, said Wednesday that he and other Democrats were committed to "the change that is needed."
Drew Hammill, a spokesman for House Speaker Nancy Pelosi, D-Calif., said the House will be looking at ways to overturn the endangered species rules and other midnight regulations.
"The House, in consultation with the incoming administration and relevant committees, will review what oversight tools are at our disposal regarding this and other last minute attempts to inflict severe damage to the law in the waning moments of the Bush administration," Hammill said.
The Bush administration has made no secret of its intent to complete the endangered species changes quickly.
When the proposal was first announced in August, the public was initially given 30 days to comment. That period was later doubled after Democratic lawmakers pressed for more time.
Then, last month, the head of the endangered species program corralled 15 experts in Washington to sort through 200,000 comments in 32 hours.
"This is definitely lightning quick," said John Kostyack, executive director of the National Wildlife Federation's Wildlife Conservation and Global Warming initiative. "I would be surprised that they spent all this time rushing it through if it wasn't greased."
If successful, the Bush administration will 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.
Supporters of the changes also expected it to be finalized later this week.
The Pacific Legal Foundation, which advocates for property rights, urged that the rules be approved.
"Litigious activists have used the Endangered Species Act to fight projects," Reed Hopper, the foundation's principal attorney, said in a statement. "The administration's current proposal is a step toward curbing these abuses."