The proposed rules, which could take effect as early as 2011, would place the greatest burden on 400 power plants, new ones and those undergoing substantial renovation, by requiring them to prove that they have applied the best available technology to reduce emissions or face penalties.

Ms. Jackson described the proposal as a common-sense rule tailored to apply to only the largest facilities  those that emit at least 25,000 tons of carbon dioxide a year  which are responsible for nearly 70 percent of greenhouse gas emissions in the United States.

The rule would not, as critics contend, cover “every cow and Dunkin’ Donuts,” Ms. Jackson said.

The move was timed to come on the same day that two Democratic senators, John F. Kerry of Massachusetts and Barbara Boxer of California, introduced global warming and energy legislation that faces a steep climb to passage this year.

The prospect of E.P.A. regulation of greenhouse gas emissions has generated fear and deep divisions within American industry. Some major utilities, oil companies and other heavy emitters are working closely with Congress to ensure that a climate bill would circumvent E.P.A. regulation by substituting a market-based cap-and-trade system. Others, led by the U.S. Chamber of Commerce and the National Association of Manufacturers, have worked against legislation and threatened to sue if the E.P.A. tries to impose controls on emissions of heat-trapping gases.

Ms. Jackson said the proposed rule had been written to exempt small businesses, farms, large office buildings and other relatively small sources of carbon dioxide emissions. But under the rule proposed Wednesday, the E.P.A. would assume authority for the greenhouse gas emissions of 14,000 coal-burning power plants, refineries and big industrial complexes that produce most of the nation’s greenhouse gas pollution.