On Friday, EPA spokeswoman Alisha Johnson confirmed that the agency would not finalize the controversial proposal on time.
Johnson said in an e-mail that the agency was still reviewing more than 2 million comments on its proposal.
"We are working on the rule and no timetable has been set," Johnson said.
EPA is likely to alter the rule in some way in an effort to make sure it can withstand a legal challenge, according to sources familiar with the matter who asked not to be identified because the standard has not been finalized. One possibility could include establishing a separate standard for coal-fired power plants, as opposed to gas-fired ones.
The rule, which the EPA proposed a year ago, would require any new power plant to emit no more than 1,000 pounds of carbon dioxide per megawatt hour of electricity produced. The average U.S. natural gas plant, which emits 800 to 850 pounds of carbon dioxide per megawatt, meets that standard; coal plants emit an average of 1,768 pounds of carbon dioxide per megawatt.
But some utilities have objected to the restrictions, complaining that even some natural gas plants will not be able to meet the new standards easily.
Will environmentalists complain about the delay, or accept it? Right now, they're waiting for a clear signal from the administration on climate. EPA acting administrator Bob Perciasepe told reporters this week the agency will start working on a rule for existing plants sometime in fiscal year 2014, though he did not give a specific timeline for when such an effort would be finished.
Union of Concerned Scientists senior climate economist Rachel Cleetus wrote a blog post Friday emphasizing the importance of finalizing the new carbon limits soon so the agency can move onto capping greenhouse gas emissions from existing plants.
"We know that in the absence of Congressional action, this is one of the most important things the administration can do to cut global warming emissions," she said in an interview. "What we need to hear from them is even with this delay, they have a firm timeline and plan for delivering on the rules for new power plants and existing power plants within this fiscal year. We need to hear those specifics."
"Missing the deadline is one thing," Cleetus added, "but if we hear dead silence, that will be truly troubling."