Rep. Richard Pombo of California, chairman of the House of Representatives natural resources committee, is expected to introduce legislation this session to revamp the law.

Activists on both sides of the issue say there is little chance of truly gutting the act given its mission of saving plants and animals, but environmentalists fear it could become significantly watered down.

When the 30-year-old act became law, most Americans saw it as a way to save great species -- charismatic megafauna such as the bald eagle or the grizzly bear. Currently 518 US species are listed under the Endangered Species Act.

But business leaders say it imposes rules and protections that cost them money and halt commerce.

"I think that the chances for improving and modernizing the act are very high in this Congress," said Jim Sims of The Partnership for the West, a business group that advocates changing the act.

Problems arise for business in areas that are habitat to a species listed as endangered under the act. Logging, oil and gas drilling are halted and roads cannot be built; recreational activity can be curtailed.

For example, as a result of the act's restrictions, a California school district faced a $1 million costly delay in building a school, and farmers in the Klamath Basin in Oregon lost up to $54 million because of restrictions on activities, according to a study conducted for the Property and Environment Research Center in Bozeman, Montana.

The most controversial proposal is change the law so it requires the use of "best science" rather than "best available science" to determine if a species is endangered. If the current research weren't conclusive, then more studies would have to be done, which would likely delay the listing of a species.

"It should be a duty on the part of the agency to fill in the gaps and do some additional studies if it doesn't have good substantial information," said M. Reed Hopper, an attorney with the The Pacific Legal Foundation which represents the rights of private landowners.

FAIRY SHRIMP, ALLIGATORS AND BEARS

Right now any citizen can petition the US Fish and Wildlife Service to list a plant or animal species. If available science shows the species is in trouble, the service will begin the steps to have it listed.

Critics say that means a species is listed without much documentation. An application to list the fairy shrimp which lives in vernal pools in the central valley of California was not much more than a one-page letter, Hopper said.

Colorado Gov. Bill Owens, chairman of the Western Governors' Association, said recently that the Endangered Species Act has been a failure at its mission of bringing back species and must be changed.

"More than 1,000 species have been listed under the act, but less than 1 percent has been successfully recovered,' Owens told a business group.

But there have been success stories. The grizzly bear is doing well and other species are recovering like the alligator, the brown pelican and the gray wolf in the Rocky Mountains.

Jeff Eisenberg, director of federal lands for the National Cattlemen's Beef Association -- which contends with the act's restrictions on grazing lands -- said species tend to stay on the list indefinitely. "All kinds of species are on there forever. There's no organized effort to get them off."

Another proposed change is to require that requests to conduct certain activities on private land affected by the act be answered within a certain time.