The Environmental Protection Agency unveiled a final rule on Thursday for regulating major emitters of greenhouse gases, like coal-fired power plants, under the Clean Air Act.

Starting in July 2011, new sources of at least 100,000 tons of greenhouse gases a year and any existing plants that increase emissions by 75,000 tons will have to seek permits, the agency said.

In the first two years, the E.P.A. expects the rule to affect about 15,550 sources, including coal-fired plants, refineries, cement manufacturers, solid waste landfills and other large polluters, said Gina McCarthy, the agency’s assistant administrator.

She said the rule would apply to sites accounting for about 70 percent of the nation’s greenhouse gas emissions. “We think this is smart rule-making, and we think it’s good government,” she said.