An important plan of the new health care law will soon be implemented by the Obama administration when standards are issued for health insurance exchanges.
These are the markets where consumers and small businesses will be able to buy coverage from competing private plans.
In order to encourage states set up the exchanges, federal officials said, they will give state officials wide leverage to decide on the operational details.
However, they said that they would intervene to set up and operate an exchange in a state, if it refused to do so.
Federal officials said the rules showed how President Obama was moving to expand insurance coverage, even as critics attacked the health care law in Congress, in court and in campaigns for the White House and Congress.
The rules, to be issued within days, were described by two officials: Kathleen Sebelius, the secretary of Health and Human Services (HHS) and Timothy B. Hill, a senior official at the department.