“If the administration gets it wrong, we’re looking at years of litigation, legislation and public and business outcry,” said a senior administration official who asked not to be identified so as not to provide an easy target for the incoming Republicans. “If we get it right, we’re facing the same thing.”

“Can we get it right?” this official continued. “Or is this just too big a challenge, too complex a legal, scientific, political and regulatory puzzle?”

The immediate effect on utilities, refiners and major manufacturers will be small, with the new rules applying only to those planning to build large new facilities or make major modifications to existing plants. The environmental agency estimates that only 400 such facilities will be affected in each of the first few years of the program. Over the next decade, however, the agency plans to regulate virtually all sources of greenhouse gases, imposing efficiency and emissions requirements on nearly every industry and every region.

Lisa P. Jackson, administrator of the E.P.A., has promised to pursue a measured and moderate course. The agency announced last week that it would not even begin issuing standards for compliance until the middle of 2011, and when it did so the rules would not impose unreasonable costs on industry.

But the reaction in Congress and industry has been outsized, with some likening the E.P.A. to terrorists and others vowing to choke off the agency’s financing for all air-quality regulation. A dozen states have filed suit to halt the new greenhouse gas rules, with one, Texas, flatly refusing to comply with any new orders from Washington.

Two federal courts, including one this week in Louisiana, have refused to issue restraining orders halting the implementation of the new rules. But late Thursday, a federal appeals court in Washington temporarily blocked the the E.P.A. from enforcing its rules in Texas while the courts consider whether the federal agency has the right to take over the Texas program. The courts have not yet ruled on the legality of the broader federal program.

Representative Fred Upton, the Michigan Republican who is set to become chairman of the powerful House Energy and Commerce Committee, said he was not convinced that greenhouse gases needed to be controlled or that the E.P.A. had the authority to do so.