WASHINGTON — The Obama administration took a big step on Tuesday to carry out the new health care law by defining “essential health benefits” that must be offered to most Americans and by allowing employers to offer much bigger financial rewards to employees who quit smoking or adopt other healthy behaviors.

The proposed rules, issued more than two and a half years after President Obama signed the Affordable Care Act, had been delayed as the administration tried to avoid stirring criticism from lobbyists and interest groups in the final weeks of the presidential campaign.

Insurance companies are rushing to devise health benefit plans that comply with the federal standards. Starting in October, people can enroll in the new plans, for coverage that begins on Jan. 1, 2014.

The rules translate the broad promises of the 2010 law into detailed standards that can be enforced by state and federal officials. Under the rules, insurers cannot deny coverage or charge higher premiums to people because they are sick or have been ill. They also cannot charge women more than men, as many now do.