Washington ? The Obama administration moved closer Monday to issuing regulations on greenhouse gases, a step that would enable it to limit emissions across the economy even if Congress fails to enact climate legislation.

The move, which coincided with the first day of the international climate summit in Copenhagen, seemed timed to reassure delegates there that the United States is committed to reducing its emissions even if domestic legislation remains bogged down. But it provoked condemnation from key Republicans and from U.S. business groups, which vowed to tie up any regulations in litigation.

In Monday’s much-anticipated announcement, the Environmental Protection Agency said that six gases, including carbon dioxide and methane, pose a danger to the environment and health of Americans and that the agency would start drawing up regulations to reduce those emissions.

“These are reasonable, common-sense steps,” said EPA Administrator Lisa Jackson, adding that they would protect the environment “without placing an undue burden on the businesses that make up the better part of our economy.” At the same time, however, EPA regulation is no one’s preferred outcome — not even the EPA’s. Jackson said her agency and other administration officials would still prefer if Congress acted before they did.

Sen. John F. Kerry, D-Mass., a leading proponent of a Senate climate bill, issued a statement after the EPA’s announcement saying, “The message to Congress is crystal clear: Get moving.”

The EPA’s “endangerment finding” — a key bureaucratic step in the regulatory process — was seen as a message to Congress and Copenhagen, but it was also a belated response to an order from the U.S. Supreme Court, which ruled in April 2007 that carbon dioxide should be considered a pollutant under the Clean Air Act. As a result, the court said, the EPA had not only the power but the obligation to regulate the gas.

Michael Morris, chief executive of American Electric Power, a utility that is the nation’s largest emitter of greenhouse gases, said Monday that “we have been a proponent … to a congressional approach to this undertaking. This is the most awkward way we could go about it.” The EPA had to comply with direction from the courts, Morris said, but “there are better approaches, more cost-effective approaches and more productive approaches.”

It remains unclear whether the EPA’s regulatory cudgel will spur Congress to take faster action on the climate legislation that is now mired in the Senate or whether it will provoke a backlash.

“The stick approach isn’t going to work. In fact, Congress may retaliate,” said Mark Helmke, a senior adviser to Sen. Richard Lugar, R-Ind. “They could stop the funding, and they could change the law.”