A legal battle is looming between environmentalists and developers over the future of the jumping frog immortalised by Mark Twain.

The dispute, which centres on urban sprawl in northern California, is one of many ecological struggles across the US and comes as conservationists warn that President Bush's policies threaten a whole host of endangered species.

The California red-legged frog ( Rana aurora draytonii ), was made famous in Twain's 1865 book, The Celebrated Jumping Frog of Calaveras County, in which the creature is the subject of a bet about its jumping prowess. "You never saw a frog so modest and straightfor'ard," wrote Twain.

But the Home Builders Association of Northern California and other property interests have filed a lawsuit seeking to overturn a US Fish and Wildlife Service decision to reserve 4.1m acres (more than 6,000 square miles) of critical frog habitat. The protected areas include many wetlands in the San Francisco Bay Area, prime development land for the expanding city.

"This lawsuit is a concerted effort by powerful development interests to undo new protections for the streams and wetlands called 'home' by Twain's frog," said Bruce Nilles, a lawyer for Earthjustice.

"Rather than provide for California's housing needs with a balanced approach that protects our natural heritage, the developers are seeking a free pass to pave over our last remaining open spaces valued by the frog and Californians."

The frog is not alone in its battle for survival. "It is very sad and very ironic to us that the Home Builders Association would take this kind of action," said Robert Stack, the director of the Calaveras county-based Jumping Frog Research Institute. "Who would even want to buy a home built on top of the wreckage of this famous frog's habitat?"

Environmentalists say that the frog - listed as endangered in 1996 - is on the verge of extinction: 90% of the state's wetlands have made way for housing, mining or other commercial interests and the frog has fled 70% of its former habitat.

Developers say that increasingly unrealistic restrictions are being put on urban growth, pushing up house prices.

But conservationists claim that the frog is only one of many creatures under threat from President Bush's policies.

The Conservation in Action report, released by the Endangered Species Coalition, detailed the need for adequate funding of the Endangered Species Act (ESA), claiming that the US is facing an "extinction crisis".

Brock Evans, executive director of the coalition, said: "Most Americans want their endangered species to be protected - so that's why the Bush administration is now seeking to gut the Endangered Species Act in secret back rooms, with no votes taken and no one held accountable."

Brian Vincent, California organiser for American Lands, said that the Bush administration was "openly hostile to the ESA - private property rights and industry are sacrosanct".

Other species listed as under threat in the report include Cerulean warblers, Aleutian sea otters, New England cottontails and wolverines.

Polls show 87% of Americans back strong protection of such species, but there is a ready market for new property away from the major cities.