EPA administrator Gina McCarthy testifies before the House Subcommittee on Energy and Power on Capitol Hill in September 2013.

The Environmental Protection Agency on Friday proposed the first-ever limits on greenhouse gas emissions from new power plants. The much-anticipated announcement brings the agency one step closer to fulfilling a key pillar of President Obama's sweeping climate plan — cutting carbon pollution from both new and existing power plants.

Speaking before reporters at the National Press Club, EPA Administrator Gina McCarthy touted the agency's plan as "one of the most significant actions we can take" to protect public health and the environment from the dangers of climate change. "By taking commonsense action to limit carbon pollution from new power plants we can slow the effects of climate change and fulfill our obligation to ensure a safe and healthy environment for our children," McCarthy said.

Noting the "really long lifetimes" of power plants, McCarthy explained that "people are making decisions about these plants today, and that is why we need to act today." The standards, the administrator added, would "ensure a clear path forward for a full energy mix."

Under the proposal, the EPA would require one standard for large natural gas plants, allowing an emissions rate of 1,000 pounds of carbon dioxide per megawatt hour of power generated. Another, slightly less restrictive standard would apply to coal-fired facilities, allowing a carbon dioxide emissions rate of 1,100 lbs. per megawatt hour.

EPA air officials say a modern gas plant could meet the standard but not its coal counterpart. Under the plan, the agency would require future coal plants to install equipment for capturing and storing carbon pollution on a partial scale, which officials call "a simpler, less costly way to reduce carbon emissions."

Agency officials present their proposal as "both flexible and achievable." They point to the construction of four coal plants that will feature carbon capture and storage technology as proof that this equipment is available and ready for use. As with most technologies, they say, the cost will likely become more affordable over time.

The proposed rule essentially mirrors emissions standards that the EPA put forth in March 2012, setting off a fierce lobbying frenzy among coal companies and coal-burning utilities opposed to what they consider to be an effective ban on coal plants. Opponents say this latest proposal would have pretty much the same effect.

"We don't believe there will be any new coal plants because of this rule," Paul Bailey, of the American Coalition for Clean Coal Electricity, the coal industry's most public voice, said Friday. "We think this rule is really bad for coal plants and it's really bad for carbon capture and storage, too."

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Such technology, coal advocates say, has yet to be commercially proven. They note that none of the four coal plants EPA officials cite are operating — two are under construction and two are under development. For the most part, they argue, these are government-funded demonstration projects whose conditions cannot be replicated at coal plants across the country.

"Until a few months ago, no one would have believed that the EPA would have claimed that carbon capture was demonstrated technology," said Jeffrey Holmstead, who represents coal and utility companies at the D.C. lobbying firm Bracewell & Guiliani.

Calling the new EPA plan "surprisingly aggressive," he noted that the agency's 2012 proposal declined to make such a claim. He predicted the coal and utility industries will fight the agency's reliance on nascent technology as a basis for an emissions standard.

"There will certainly be a big debate over this," added Holmstead, who headed the EPA's air office under President George W. Bush. "If EPA says, 'This is the standard,' there will be litigation."

In a statement, Trip Van Noppen, president of the environmental law firm Earthjustice, called the EPA proposal "welcome news. Tackling carbon pollution from power plants is critical to addressing the climate crisis that we now face."

The EPA proposal must go through a 60-day public comment period, and the agency plans to hold a public hearing.