WASHINGTON — The Obama administration announced new steps to expand coverage under the federal health care law on Monday, less than a week after the Government Accountability Office, a nonpartisan investigative arm of Congress, found that the federal government and many states were "behind schedule" in setting up marketplaces where Americans are supposed to be able to buy insurance. The steps — establishing a Web site and a telephone call center to provide information to consumers — are in preparation for what the government anticipates will be a flood of people buying health insurance starting Oct. 1.