WASHINGTON --Two White House officials say Carol Browner is stepping down as President Barack Obama's chief adviser on energy and climate matters. Browner's resignation is expected to happen in the coming weeks. The officials said she will stay on as needed to ensure a smooth transition. The officials spoke on condition of anonymity because the personnel move had not been announced. Browner has been a central figure in the White House's strategy of trying to get a comprehensive energy bill passed, a matter that has stalled on Capitol Hill. She was also a prominent voice in the administration's response to the massive oil spill in the Gulf of Mexico last year. Her resignation comes amid a series of high-profile staff changes in Obama's White House.