Washington (Platts)--18Jan2013/347 pm EST/2047 GMT

A top official at the US Environmental Protection Agency declined Friday to say when the agency would tackle greenhouse gas emissions through Clean Air Act standards for existing fossil-fuel burning power plants under a second Obama administration, but indicated that controls for new generating units would be done first.

"We have to finish the new sources first," EPA Deputy Administrator Bob Perciasepe told reporters when asked whether the agency planned to pursue carbon dioxide standards for existing power plants during the next four years.

Perciasepe, who discussed stormwater issues on a panel at the United States Conference of Mayors' Winter Meeting, declined to answer further questions about when EPA might act on a GHG rulemaking for the nation's current fleet of coal-fired generation.

The agency, in an agreement with environmental groups, last spring proposed GHG new source performance standards for the next generation of coal-fired power plants and is expected to finalize them in the first half of this year. EPA, however, has declined to confirm it would proceed with a GHG NSPS rulemaking for existing coal plants.

Perciasepe is expected to serve as acting administrator until a new EPA chief is nominated by President Barack Obama and confirmed by the US Senate. Current EPA Administrator Lisa Jackson, who led the agency in setting the first GHG rules on new power plants and vehicles, said she will leave the administration after the president's State of the Union address.

--Cathy Cash, cathy_cash@platts.com --Edited by Jason Lindquist, jason_lindquist@platts.com