For another year, the confluence of partisan tensions, ideological differences, regional conflicts and interest group politics has blocked action on key environmental legislation including reducing air pollution and protecting endangered species, according to lawmakers, advocates and academics.

Some analysts warn that the long-standing impasse is reaching a crisis point, as some federal programs are running low on funds and public health threats such as asthma and respiratory problems and pollution of lakes and streams are rising. The stalemate has prompted the Bush administration to resolve environmental questions through changes in federal regulations, effectively leaving Congress on the sidelines.

"We are in a stalemate," said House Resources Committee Chairman Richard W. Pombo (R-Calif.). He said that although he resents the executive branch's growing influence on environmental issues, "we've allowed it to happen. We never should have."

Congress adjourned last week without having acted on a number of key measures, including the president's Clear Skies proposal for reducing power plant emissions; efforts to renew an expired industry tax to fund the cleanup of toxic Superfund sites; limits on heat-trapping gases linked to global warming; and measures to alter federal protections of endangered species.

Last year, Congress approved the administration's Healthy Forests initiative aimed at controlling forest fires by increasing logging on selected federal lands. It also previously approved administration-backed legislation to clean up blighted industrial sites, known as "brownfields" and authorized $40 billion of conservation programs over the coming decade as part of a 2002 farm bill. But for the most part, Congress has had a dismal record of inaction on important environmental issues.

Emblematic of the congressional standoff is the Senate Environment and Public Works Committee, where the top two senators have been unable to agree to meet in the same room to approve minor bills. The political and ideological chasm is evident in how they discuss environmental issues: Committee Chairman James M. Inhofe (R-Okla.) describes environmentalists this way: "They are really liberals. They're all strong pro-abortionists, they're all pro-gun control people, flying under the flag of environmentalism." Ranking minority member James M. Jeffords (I-Vt.) says President Bush is "killing people" because he won't crack down on pollution from power plants.

Although he promised action on the measure, Inhofe has yet to hold a committee vote on the president's Clear Skies initiative, which Bush says would reduce harmful sulfur dioxide and nitrogen oxide emissions 70 percent by 2018. Moreover, just two Republicans have co-sponsored the legislation in the Senate, an indication of the lack of interest in a measure the administration touted as a top priority.

Both sides say the government needs to do more to curb pollution from coal-fired power plants, which generate half the nation's electricity but account for 90 percent of the industry's pollution, according to federal estimates. But many environmentalists and Democrats say that federal law calls for steeper and faster pollution curbs than contained in the president's plan and that Congress should also limit carbon dioxide emissions that are linked to global warming.

The utility industry -- which has donated $34 million to federal candidates since Bush took office, two-thirds of which went to Republicans -- has resisted regulation but prefers Bush's plan to other proposals. The outlook is also dim for a bill sponsored by Sens. John McCain (R-Ariz.) and Joseph I. Lieberman (D-Conn.) that would curb emissions linked to global warming.

McCain said in an interview that his bill has been blocked by "the power and influence of the special interest lobby, especially public utilities and automobile manufacturers," but he was confident public opinion would eventually overcome the opposition. "The question is, how much damage is done before that happens?" he said.

Mark Whitenton, the National Association of Manufacturers' vice president for resources and environmental policy, said that his members want certainty on emissions rules but that he doesn't expect Clear Skies to pass for another four years. "As long as the parties stay close [in Congress], everybody's playing for the election instead of doing good for the country," he said.

Other environmental initiatives have languished for years on Capitol Hill. The Endangered Species Act has remained unchanged for 30 years. The nation's Superfund program, which aims to clean up toxic waste sites but is facing historic budget shortfalls, has not been reauthorized in nearly two decades.

"It's really irksome," said Natural Resources Defense Council advocacy director Greg Wetstone, who has worked on environmental legislative issues on and off the Hill for more than two decades. "What's broken is a political system that's evading science, fact and public opinion."

Although officials of both the Clinton and Bush administrations have opted to regulate in the face of congressional inaction, even some of Bush's top appointees have questioned this approach.

Environmental Protection Agency Administrator Mike Leavitt notes that as the debate over Clear Skies has dragged on, more than 470 counties are failing to meet federal air quality standards. As a result, he said, he has no choice but to push ahead with new rules -- even though some critics have attacked them for not being strict enough.

"Legislation would have been far superior to a regulatory action," Leavitt said. "But [lawmakers] have not been forthcoming. And we can't afford to wait."

Steven Hayward, a resident scholar at the conservative American Enterprise Institute, says both sides deserve blame for the gridlock. Conservatives are too quick to criticize environmental initiatives without articulating what they can support, he said. Meanwhile, environmentalists fail to give Republicans credit for their efforts, such as when President George H.W. Bush helped shepherd clean air legislation into law in 1990.

"What was a consensus issue is now a bitter partisan issue," Hayward said.

Senate Environment and Public Works Committee Chairman James M. Inhofe has not held a panel vote on President Bush's Clear Skies initiative, despite vowing action on the measure. Sen. James M. Jeffords, the panel's ranking minority member, and Inhofe can't agree to meet in the same room to vote on minor bills. The panel's problems are symbolic of the impasse.