WASHINGTON (AP) -- The Environmental Protection Agency has concluded that carbon dioxide and five other greenhouse gases are a danger to public health and welfare, taking the first step to regulating pollution linked to climate change, The Associated Press has learned.

Such regulation would have widespread economic and social impact, from requiring more fuel efficient automobiles to limiting carbon dioxide emissions from power plants and industrial sources, changing the way the nation produces energy.

The EPA will announce its proposed finding Friday, triggering a 60-day comment period before issuing a final ruling, said congressional officials who have been briefed by the agency. They spoke on condition of anonymity because an announcement had not yet been made.

The EPA has concluded that the science pointing to man-made pollution as a cause of global warming is “compelling and overwhelming.” The blame goes mainly to carbon dioxide from burning fossil fuels.

The six greenhouse gases “pose a threat to public health and welfare,” the EPA has determined. It also will say tailpipe emissions from motor vehicles contribute to climate change.

The EPA action was prompted by a Supreme Court ruling two years ago that said greenhouse gases are pollutants under the Clean Air Act and must be regulated if found to be a danger to human health or public welfare.

The Bush administration strongly opposed using the Clean Air Act to address climate change and stalled on producing the so-called “endangerment finding” demanded by the high court in its April 2007 ruling.

The court case, brought by Massachusetts, focused only on emissions from automobiles. But it is widely assumed that if the EPA must regulate emissions from cars and trucks, it will have no choice but to control identical pollution from power plants and industrial sources.

While the EPA clearly indicates by its action Friday that it is ready to pursue regulation under the Clean Air Act to address the threats of global warming, the agency also will say that it prefers the problem be dealt with more broadly by Congress, the officials said.

Congress is considering imposing an economy-wide cap on greenhouse gas emissions along with giving industry the ability to trade emission allowances to mitigate costs.

Legislation could be considered by the House before the August congressional recess.