Reuters reported earlier Monday that a delay was likely.
EPA has already missed deadlines earlier this year to propose greenhouse gas standards for power plants.
EPA Administrator Lisa Jackson told the program "energyNow!" in an interview broadcast over the weekend that the power plant rules should be proposed early next year.
The rules are among a number of controversial Clean Air Act rules that EPA is rolling out amid resistance from Republicans and industry groups.
The agency is slated to finalize standards for power plant emissions of mercury and other air toxics in mid-December. An agency spokeswoman said in an email Monday that “we're still on” to release the "Maximum Achievable Control Technology" standards for power plants on Dec. 16.