By Valerie Volcovici
WASHINGTON, Feb 21 (Reuters) - Gina McCarthy, said to be U.S. President Barack Obama's choice as the nation's top environmental regulator, avoided questions about a potential promotion on Thursday but said states will play a key role in shaping federal regulations at an energy and climate policy forum.
McCarthy, assistant administrator for the U.S. Environmental Protection Agency's Office of Air and Radiation since 2009, was tightlipped about whether Obama will nominate her as the EPA's next administrator.
Sources told Reuters on Wednesday that Obama would nominate the Boston native as early as this week, with a formal announcement more likely next week.
Thursday's appearance was the first public event for McCarthy, 58, since speculation arose that she will replace Lisa Jackson, the EPA administrator who stepped down this month, as the face of Obama's fresh push to fight climate change.
Addressing a room full of familiar faces at a workshop of state and federal regulators, McCarthy applauded local efforts, such as the nine-state carbon cap-and-trade program in the Northeast United States, for showing Washington a path forward on combating climate change.
"At the EPA we will do our part to build on your success," she said at the Georgetown University Law Center.
"We can find a way instead of having national solutions...to open up opportunities for states to use all the flexibility, the ingenuity, the innovation that you have shown could be done, and just simply get it done."
The EPA is expected to complete the rule this spring on emissions standards for new power plants. McCarthy said the agency is still reading over 1 million public comments that the proposal has received.
McCarthy recalled that she attended the same conference four years ago, when still working for the Connecticut Department of Environmental Protection.
"We were suing the EPA to recognize greenhouse gases as a pollutant that needed to be regulated under the Clean Air Act," she quipped.
McCarthy came to Washington after serving as the top state environmental regulator in Massachusetts and Connecticut under Democratic and Republican governors.
She was as environmental policy adviser to then-Massachusetts Governor Mitt Romney and launched the state's first Climate Protection Action Plan.
Romney was Obama's Republican opponent in the 2012 presidential election and a regular critic of the EPA.
(Reporting By Valerie Volcovici; Editing by Ros Krasny and Lisa Shumaker)